A highly efficient nitrogen and phosphorus removal system for treating aquaculture tail water

Abstract

The invention provides a high-efficiency nitrogen removal and phosphorus removal system for treating aquaculture tail water. The system comprises a tail water treatment biological filter, a suspended filler, a direct current positive and negative electrode array combination, an electric stirring device and a carbon source supplement device. The suspended filler is arranged in the tail water treatment biological filter, the direct current positive and negative electrode array combination is arranged on the upper part of the tail water treatment biological filter, the electric stirring device is arranged on the lower part of the tail water treatment biological filter, a sludge hopper is arranged at the bottom of the tail water treatment biological filter, the electric stirring device is arranged above the sludge hopper, and the carbon source supplement device is connected to the tail water treatment biological filter through a pipeline; the volume ratio of the suspended filler to the water body in the tail water treatment biological filter is 20% to 50%, and the density of the suspended filler is 0.92 to 0.98 g / cm 3 The present invention has the advantages of high denitrification and dephosphorization efficiency, small footprint, no need for air pump oxygenation, energy saving, low cost, no secondary pollution, and simple management.

Description

[Technical field]

[0001] The invention relates to a high-efficiency nitrogen and phosphorus removal system for treating aquaculture tail water. [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%. However, pond aquaculture tailwater and factory aquaculture tailwater are basically discharged directly without treatment. Since aquaculture tailwater generally contains high nitrogen and phosphorus, it leads to varying degrees of eutrophication pollution in the surrounding water environment. In order to protect the ecological environment of the water area, both governments at all levels and society require that aquaculture tailwater must be treated so that the water quality of the discharged water can meet the relevant national environmental protection requirements, such as the "Freshwater Aquaculture Tailwater Discharge Requirements" (SC / T 9101), the national "Surface Water Environmental Quality Standard" (GB3838-2002) Class III water quality standards, and the "Seawater Aquaculture Tailwater Discharge Requirements" (SC / T 9103). 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, etc. for nitrogen and phosphorus removal. Although there is a certain nitrogen and phosphorus removal effect, there are problems such as large land occupation, low nitrogen and phosphorus removal efficiency, high operating cost, poor treatment effect stability, 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 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 an efficient denitrification and phosphorus removal system for treating aquaculture tail water, which has the advantages of high denitrification and phosphorus removal efficiency, small footprint, no need for air pump oxygenation, energy saving, low cost, no secondary pollution, and easy management.

[0005] The present invention is achieved in that:

[0006] A highly efficient denitrification and dephosphorization system for treating aquaculture tail water, the system comprising a tail water treatment biological filter, a suspended filler, a DC anode and cathode electrode array combination, an electric stirring device and a carbon source supplement device, the suspended filler is arranged in the tail water treatment biological filter, the DC anode and cathode electrode array combination is arranged at the upper part of the tail water treatment biological filter, the electric stirring device is arranged at the lower part of the tail water treatment biological filter, a sludge hopper is arranged at the bottom of the tail water treatment biological filter, the electric stirring device is arranged above the sludge hopper, and the carbon source supplement device is connected to the tail water treatment biological filter through a pipeline;

[0007] The volume ratio of the suspended filler to the water in the tailwater treatment biological filter 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.

[0008] Furthermore, the suspended filler is made of high-density polyethylene with a specific surface area greater than 500m 2 / m 3 .

[0009] 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 .

[0010] Furthermore, the tailwater treatment biological filter is a combination of 2 to 3 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.

[0011] The present invention has the following advantages:

[0012] 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 aquaculture tailwater treatment pool, 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 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.

Brief Description of the Drawings

[0013] The present invention will be further described below in conjunction with embodiments with reference to the accompanying drawings.

[0014] Figure 1 The present invention is a schematic diagram of the structure of a high-efficiency denitrification and phosphorus removal system for treating aquaculture tail water. [Specific implementation method]

[0015] See also Figure 1 The present invention relates to a highly efficient nitrogen removal and phosphorus removal system for treating aquaculture tail water, the system comprising a tail water treatment biological filter 1, a suspended filler 2, a DC anode and cathode electrode array combination 3, an electric stirring device 4 and a carbon source supplement device, the suspended filler 2 is arranged in the tail water treatment biological filter 1, the DC anode and cathode electrode array combination 3 is arranged at the upper part of the tail water treatment biological filter 1, the electric stirring device 4 is arranged at the lower part of the tail water treatment biological filter 1, a sludge hopper 5 is arranged at the bottom of the tail water treatment biological filter 1, the electric stirring device 4 is arranged above the sludge hopper 5, and the carbon source supplement device is connected to the tail water treatment biological filter 1 through a pipeline 6;

[0016] The volume ratio of the suspended filler 2 to the water in the tailwater treatment biological filter 1 is 20% to 50%, and the density of the suspended filler 2 is 0.92 to 0.98 g / cm 3 ; The anode of the DC positive and negative electrode array combination 3 is iron, and the cathode is iron, carbon or copper; the rotation speed of the electric stirring device 4 is 100 to 300 r / min.

[0017] The suspended filler 2 is made of high-density polyethylene with a specific surface area greater than 500m 2 / m 3 .

[0018] The spacing between adjacent electrodes of the DC positive and negative electrode array combination 3 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 .

[0019] The tailwater treatment biological filter 1 is a combination of 2 to 3 tank bodies connected in series, and a DC positive and negative electrode array combination 3 can be set on part or all of the tank bodies.

[0020] The working principle of the present invention is as follows:

[0021] (1) Due to the DC electric field of the DC anode and cathode electrode array combination 3, 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 5 of the tail water treatment biological filter 1; 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 5 at the bottom of the tail water treatment biological filter 1.

[0022] (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 2, 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.

[0023] (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.

[0024] (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.

[0025] 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 2. 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.

[0026] (5) Using the density of the suspended filler 2 (0.92-0.98 g / cm 3 ) is close to fresh water, and is easy to form a uniform suspension state in the water body of the tailwater treatment biological filter. At the same time, under the continuous slow stirring of the electric stirring device 4 and the flow of water, a fluidized state can be formed, so that the biofilm attached to the suspended filler 2 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 2 and the water flow and the flow through the electrode surface. The density is 0.92-0.98 g / cm at the same volume. 3The 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.

[0027] (6) Microcurrent can strengthen the bacteria and other microorganisms in the biofilm on the suspended filler 2, change the permeability of the bacterial cell membrane, help the enzymes in the bacterial cell membrane to pass through the cell membrane into the wastewater for a series of enzymatic reactions, increase the contact between the enzymes in the cell membrane and the reaction substrates in the water, and thus enhance the effect of degrading nitrogen and phosphorus in 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.

[0028] (7) Since the organic carbon concentration in the aquaculture tail water is generally low and will be consumed quickly, in order to promote the heterotrophic denitrification reaction in the pool, a supplementary carbon source such as brown sugar is added. 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 6 to continuously and rapidly promote the heterotrophic denitrification reaction.

[0029] 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.

[0030] 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.

[0031] The present invention is further described below in conjunction with specific embodiments.

[0032] Applying the above system method, a tailwater denitrification and phosphorus removal treatment pool was constructed to deeply treat the tailwater of eel pond aquaculture and factory aquaculture for nitrogen, phosphorus and organic matter. The result data are as follows:

[0033]

[0034] Note: Influent refers to aquaculture tail water, and effluent refers to the discharged water after treatment in the treatment pool.

[0035] In summary, the maximum removal rate of ammonia nitrogen in the aquaculture tail water treated by the present invention is 99.4%, the maximum removal rate of total nitrogen is 96.6%, and the maximum removal rate of total phosphorus is 96%.

[0036] 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 aquaculture tailwater treatment pool, 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 sewage treatment efficiency. 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.

[0037] The ammonia nitrogen, total nitrogen, total phosphorus and permanganate index of the aquaculture tail water treated by the system of the present invention have reached the Class III water quality standard in the national "Surface Water Environmental Quality Standard" (GB3838-2002), and some have even reached the Class II water quality standard. It also meets the first-level discharge standard specified in the "Freshwater Aquaculture Tail Water Discharge Requirements" (SC / T 9101).

[0038] 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 efficient nitrogen and phosphorus removal system for treating aquaculture tail water, characterized by: The system comprises a tailwater treatment biological filter, a suspended filler, a DC anode-cnode electrode array combination, an electric stirring device and a carbon source supplement device, wherein the suspended filler is arranged in the tailwater treatment biological filter, the DC anode-cnode electrode array combination is arranged at the upper part of the tailwater treatment biological filter, the electric stirring device is arranged at the lower part of the tailwater treatment biological filter, a sludge hopper is arranged at the bottom of the tailwater treatment biological filter, the electric stirring device is arranged above the sludge hopper, and the carbon source supplement device is connected to the tailwater treatment biological filter through a pipeline; The volume ratio of the suspended filler to the water in the tailwater treatment biological filter 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 tailwater treatment 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, and the suspended filler and the water flow continuously rub and flow through the electrode surface to remove the oxide on the surface of the anode iron. The anode of 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 100-300r / min; 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 ; 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 high-efficiency nitrogen and phosphorus removal system for treating aquaculture tail water 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 high-efficiency nitrogen and phosphorus removal system for treating aquaculture tail water according to claim 1, characterized in that: The tailwater treatment biological filter is a combination of 2 to 3 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.

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