A marine aquaculture tailwater treatment system

Abstract

The present invention provides a marine aquaculture tailwater treatment system, comprising a sewage collection tank, a physical filtration device, an air flotation tank, and an electrode-suspended filler coupled biofilter treatment unit connected in sequence, wherein the sewage collection tank, the physical filtration device, the air flotation tank, and the electrode-suspended filler coupled biofilter treatment unit 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 a seawater aquaculture tail water treatment system. [Background technology]

[0002] At present, the tail water of pond aquaculture and factory aquaculture in seawater is basically discharged directly without treatment. Since the tail water of seawater aquaculture generally contains high concentrations of inorganic nitrogen, active phosphate, chemical oxygen demand COD, and suspended solids, it is easy to cause eutrophication pollution to the coastal marine environment to varying degrees. In order to protect the ecological environment of the coastal sea area, both governments at all levels and society require that the treatment of aquaculture tail water must be carried out so that the water quality of the discharged water can meet the relevant national environmental protection requirements, such as the "Discharge Requirements for Seawater Aquaculture Tail Water" (SC / T 9103) and the corresponding water quality standards in the national "Seawater Quality Standard" (GB 3097-1997). The current seawater pond aquaculture tail water or factory aquaculture tail water treatment technology mainly adopts 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 it has a certain nitrogen and phosphorus removal effect, it has the problems of large area occupation, low nitrogen and phosphorus removal efficiency, 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 are unable to carry out tailwater discharge treatment due to land area limitations and high treatment costs, polluting the surrounding marine environment or facing the problem of being forced to suspend production due to non-compliance with environmental 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 the inability to perform electrolysis normally. Regular cleaning or replacement is required, 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 a marine 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 simple management.

[0005] The present invention is achieved in that:

[0006] A marine aquaculture tailwater treatment system, characterized in that: the tailwater treatment system comprises a sewage collection tank, a physical filtration device, an air flotation tank, an electrode-suspended filler coupled biological filter treatment unit and a sludge concentration and dehydration device; the sewage collection tank, the physical filtration device and the air flotation tank are connected in sequence, the air flotation tank is connected to the electrode-suspended filler coupled biological filter treatment unit, and the sewage collection tank, the physical filtration device, the air flotation tank, the electrode-suspended filler coupled biological filter treatment unit 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; a bubble diffuser is arranged at the bottom of the flotation tank;

[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] The present invention has the following advantages:

[0014] 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 in the biofilter, integrated iron cation phosphate precipitation reaction, iron cation hydrate and its polymer flocculation precipitation on phosphorus and other particulate matter, nitrification reaction and denitrification reaction, etc. The device has the advantages of simple structure, small amount of sludge production and no secondary pollution.

[0015] The present invention solves the problems of low efficiency of denitrification and phosphorus removal in the current marine aquaculture tail water, large land occupation, and poor stability of treatment effect, and has the advantages of high denitrification and phosphorus removal efficiency, land saving, stable compliance with the "Requirements for Discharge of Marine Aquaculture Tail Water" (SC / T 9103), low investment and operation costs, and simple management. By using the device and facilities of the present invention, after the marine aquaculture tail water is treated, the inorganic nitrogen, active phosphate, chemical oxygen demand COD, suspended solids, pH and other factor indicators in the discharged water can all meet the first-level discharge standards specified in the "Requirements for Discharge of Marine Aquaculture Tail Water" (SC / T 9103).

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 structure of the electrode-suspended filler coupled biofilter treatment unit in the present invention. [Specific implementation method]

[0019] See also Figure 1-2 The present invention relates to a marine aquaculture tailwater treatment system, which comprises a sewage collection tank 1, a physical filtration device 2, an air flotation tank 3, an electrode-suspended filler coupled biological filter treatment unit 4 and a sludge concentration and dehydration device 5; the sewage collection tank 1, the physical filtration device 2 and the air flotation tank 3 are connected in sequence, the air flotation tank 3 is connected to the electrode-suspended filler coupled biological filter treatment unit 4, and the sewage collection tank 1, the physical filtration device 2, the air flotation tank 3, the electrode-suspended filler coupled biological filter treatment unit 4 are all connected to the sludge concentration and dehydration device 5;

[0020] The electrode-suspended filler coupled biofilter treatment unit 4 includes a biofilter 41, a suspended filler 42, a DC anode-cnode electrode array combination 43, an electric stirring device 44 and a carbon source supplement device 45, wherein the suspended filler 42 is arranged in the biofilter 41, the DC anode-cnode electrode array combination 43 is arranged at the upper part of the biofilter 41, the electric stirring device 44 is arranged at the lower part of the biofilter 41, a sludge hopper 46 is arranged at the bottom of the biofilter 41, the electric stirring device 44 is arranged above the sludge hopper 46, and the carbon source supplement device 45 is connected to the biofilter 41 through a pipeline; a bubble diffuser is arranged at the bottom of the flotation tank 3;

[0021] The volume ratio of the suspended filler 42 to the water in the biofilter 41 is 20% to 50%, and the density of the suspended filler 42 is 0.92 to 0.98 g / cm 3The anode of the DC positive and negative electrode array combination 43 is iron, and the cathode is iron, carbon or copper; the rotation speed of the electric stirring device 44 is 100 to 300 r / min.

[0022] The suspended filler 42 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 43 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 41 is a combination of two or more tank bodies connected in series, and a DC positive and negative electrode array combination 43 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] 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 air flotation tank 3, while the backwash water (≤1.5%) containing large particles such as residual bait and feces enters the sludge concentration and dehydration device 5; in the air flotation tank 3, some suspended matter, small and medium particles and part of soluble protein in the water overflow with the floating bubbles (≤0.5%) and are discharged into the sludge concentration and dehydration device 5, and the bottom flow water enters the electrode-suspended filler coupled biological filter treatment unit 4; in the sludge In the 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 filtered water is returned to the sewage collection tank 1; in the electrode-suspended filler coupled biological filter treatment unit 4, a sludge hopper 46 is provided at the bottom of the biological filter 41, which can discharge sewage regularly, and the sludge water (≤3%) is discharged into the sludge concentration and dehydration device 5; the effluent treated by the electrode-suspended filler coupled biological filter treatment unit 4 can meet the first-level standard of "Seawater Aquaculture Tail Water Discharge Requirements" (SC / T9103), and achieve standard discharge.

[0027] The working principle of each device is as follows:

[0028] 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.

[0029] 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 the backwash water (≤1.5%) containing large particles such as leftover bait and feces into the sludge dehydration and concentration device 5, while the water after being filtered by the screen enters the flotation tank 3.

[0030] 3. A bubble diffuser connected to an external air pump is provided at the bottom of the flotation tank 3, which can form a huge number of tiny bubbles in the water. Some suspended matter, small and medium-sized particles and some soluble proteins in the water entering the tank from the physical filtration device 2 can float up and overflow (≤0.5%) with the bubbles and be discharged into the sludge concentration and dehydration device 5, and the bottom flow water enters the electrode-suspended filler coupled biological filter treatment unit 4.

[0031] 4. The working principle of the electrode-suspended filler coupled biofilter treatment unit 4 is as follows:

[0032] (1) Due to the DC electric field of the DC anode and cathode electrode array combination 43, the iron (anode) generates a large amount of iron cations, and a large amount of Fe 2+ and Fe 3+ The phosphate in the aquaculture tail water undergoes precipitation reaction to form granular, insoluble substances that settle in the bottom sludge hopper 46 of the biological filter 41; 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 46 at the bottom of the biological filter 41. In addition, the high salinity of seawater can ensure a sufficiently large conductivity, which is conducive to reducing the energy consumption of treating seawater aquaculture tail water.

[0033] (2) Strictly control the microcurrent density between 0.1 and 1.0 mA / cm 2 , within this range, seawater electrolysis cannot produce and accumulate free chlorine or hydroxyl radicals due to low current density. It is well known that if there are free chlorine or hydroxyl radicals in seawater, they can react with organic matter to generate halogenated byproducts, among which trihalomethanes (such as chloroform, etc.) are genotoxic to farmed animals and are also carcinogens. Therefore, the present invention ensures the safety of seawater treatment, completely avoids the conventional electrochemical oxidation treatment of seawater wastewater, and the secondary pollution problem caused by the production of trihalomethanes or the need to add safe treatment facilities for trihalomethanes.

[0034] (3) The iron ions generated by the electrode can combine with the chloride ions in the seawater to form ferric chloride. Ferric chloride is a flocculant. The coagulation of FeCl3·6H2O flocs in the water can form composite flocs with some suspended matter, particulate matter and electrolytes in the water, and settle in the sludge hopper 46 at the bottom of the biological filter 41.

[0035] (4) The dissolved oxygen contained in the tail water of seawater aquaculture 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 42, thereby converting ammonia nitrogen into nitrite nitrogen and nitrate nitrogen. 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] (5) 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] (6) 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 42. 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] (7) Using the density of the suspended filler 42 (0.92 to 0.98 g / cm 3 ) is close to seawater, 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 44 and the flow of water, a fluidized state can be formed, so that the biofilm attached to the suspended filler 42 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 42 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] (8) Microcurrent can strengthen the bacteria and other microorganisms in the biofilm on the suspended filler 42, 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] (9) 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 45. 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 it to the pool through a metering pump and a certain amount through a pipeline to continuously and rapidly promote the heterotrophic denitrification reaction. Since the reaction rate of heterotrophic denitrification is several times (about 7 times) faster than that of autotrophic denitrification, and at the same time, the population growth and expansion rate of heterotrophic denitrifying bacteria are higher than that of autotrophic denitrifying bacteria. Therefore, adding supplementary organic carbon sources such as brown sugar can significantly accelerate denitrification.

[0042] 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.

[0043] 5. 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.

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

[0045] A seawater aquaculture tailwater treatment system constructed by the present invention is used to treat tailwater from seawater pond aquaculture and factory aquaculture of large yellow croaker. The quality of the discharged water after treatment meets the requirements. The monitoring result data are as follows:

[0046]

[0047] Note: Influent refers to the tail water of marine aquaculture, and effluent refers to the discharged water after treatment in the treatment pool.

[0048] In summary, the inorganic nitrogen, active phosphate, chemical oxygen demand COD, pH, suspended solids, etc. in the discharged water of marine aquaculture tail water after being treated by the treatment system of the present invention all meet the first-level discharge standards specified in the "Discharge Requirements for Marine Aquaculture Tail Water" (SC / T 9103).

[0049] In summary, 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 precipitation of phosphorus and other particulate matter, nitrification reaction and denitrification reaction, etc. The device has the advantages of simple structure, small amount of sludge production and no secondary pollution.

[0050] The invention solves the problems of low denitrification and phosphorus removal efficiency, large floor space and poor stability of treatment effect in the current marine aquaculture tail water. The invention has the advantages of high denitrification and phosphorus removal efficiency, land saving, stable compliance with the "Marine Aquaculture Tail Water Discharge Requirements" (SC / T 9103), low investment and operation costs, simple management and the like.

[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. A marine aquaculture tailwater treatment system, characterized in that: The tailwater treatment system comprises a sewage collection tank, a physical filtration device, an air flotation tank, an electrode-suspended filler coupled biological filter processing unit and a sludge concentration and dehydration device; the sewage collection tank, the physical filtration device and the air flotation tank are connected in sequence, the air flotation tank is connected to the electrode-suspended filler coupled biological filter processing unit, and the sewage collection tank, the physical filtration device, the air flotation tank, the electrode-suspended filler coupled biological filter processing unit 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; a bubble diffuser is arranged at the bottom of the flotation tank; 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. The 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, 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 aquaculture wastewater. In addition, the microcurrent directly stimulates the activity of the extracellular enzymes secreted by the strengthened bacteria, promoting the degradation of nitrogen, phosphorus and other pollutants in the water.

2. A marine 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. A marine 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. A marine 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.

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