Method for denitrification of mariculture tail water under micro-aerobic conditions

Abstract

The application discloses a seawater breeding tail water denitrification method under a micro-aerobic condition, which combines an iron-carbon micro-electrolysis system and a microbial denitrification system to jointly denitrify seawater breeding tail water. Under the optimized micro-aerobic condition provided by the application, the iron-carbon micro-electrolysis system and the microbial denitrification system produce a synergistic effect, and the nitrogen removal rate is improved. Compared with the prior art in which the iron-carbon micro-electrolysis system and the microbial denitrification system jointly denitrify, the same or even better nitrogen removal rate can be achieved only by using a shorter time and simple reaction conditions.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for denitrification of marine aquaculture tailwater under micro-aerobic conditions. Background Technology

[0002] In recent years, China has made significant progress in aquaculture. In 2022, the output value of my country's aquaculture industry reached 1,250.187 billion yuan, a year-on-year increase of 6.2%; the marine aquaculture area was 2,074,420 hectares, a year-on-year increase of 2.4%; and the output of marine aquaculture products was 22.757 million tons, a year-on-year increase of 2.9%. However, with the rapid expansion of high-yield, high-density aquaculture, harmful substances are generated from the decomposition of residual feed and excrement, leading to water quality deterioration, harming the health of aquatic organisms, and seriously hindering the sustainable development of marine aquaculture. Therefore, the treatment of marine aquaculture wastewater and the development of marine aquaculture wastewater treatment technologies have become urgent issues for the green development of marine aquaculture, and are indispensable tasks for maintaining the ecological health of aquaculture waters and the sustainable development of the aquaculture industry.

[0003] In the middle and later stages of high-density aquaculture, the maximum feed input needs to be met. A large amount of nitrogen remains in the aquaculture water along with uneaten feed and feces, and nitrogen gradually accumulates. The C / N ratio decreases as the aquaculture production process progresses. Therefore, the tailwater of marine aquaculture is characterized by a low C / N ratio.

[0004] Biological treatment technology is a widely applicable, stable, and safe technology. Its principle is mainly to introduce organisms with certain cleaning capabilities into the wastewater of aquaculture to purify the water. Although biological treatment is widely used in water treatment due to its high efficiency and economic feasibility, even well-adapted microorganisms can only treat relatively low concentrations of pollutants. High concentrations of chemicals can also inhibit the growth and reproduction of microorganisms. Therefore, the removal effect of microorganisms alone on nitrogenous pollutants in marine aquaculture wastewater is limited. The removal rate of ammonia nitrogen was 49.52%, nitrate nitrogen 66.21%, and nitrite nitrogen 68.40%, but the total nitrogen removal rate was only a maximum of 37.69%, which needs further improvement. Furthermore, the denitrification performance of traditional biological treatment technology is affected by the presence or absence of aerobic conditions. Denitrification consists of two processes: nitrification and denitrification. Nitrification refers to the process of oxidizing ammonia nitrogen to nitrate nitrogen by nitrifying bacteria under aerobic conditions, while denitrification refers to the process of reducing nitrite and nitrate to gaseous nitrogen by denitrifying bacteria under anaerobic conditions. Against this backdrop, further exploration is still needed to promote traditional microbial denitrification and achieve efficient simultaneous nitrification and denitrification.

[0005] CN112047456A proposes a microbial fuel cell wastewater denitrification device and method. The device is divided into a microcathode chamber and an anode chamber. The cathode chamber is filled with bio-ceramic filler and iron-carbon micro-electrolysis filler. By alternately introducing air and carbon dioxide into the cathode, alternating between anaerobic and aerobic conditions, nitrification and denitrification occur at the cathode. This device achieves an ammonia nitrogen removal rate of 69.4-90.7% and a total nitrogen removal rate of 59.2-80.1%, demonstrating better denitrification performance compared to traditional microbial denitrification methods. However, it requires dividing the device into two chambers and intermittent aeration of the cathode chamber, making the device and operation relatively complex, requiring multiple materials, and necessitating a reaction time of over 24 hours. Further optimization is still needed. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and provide a method for denitrification of marine aquaculture tailwater under microaerobic conditions.

[0007] The technical solution of the present invention is as follows:

[0008] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0009] (1) Add nitrifying bacteria, denitrifying bacteria and iron-carbon filler to the effluent of seawater aquaculture, mix well and obtain reaction solution;

[0010] (2) After introducing dissolved oxygen into the reaction solution, the reaction is carried out for 2-24 hours to obtain a mixed solution;

[0011] (3) Remove the solids from the above mixture to obtain denitrified seawater aquaculture tailwater;

[0012] The amount of iron-carbon filler added is 5-10 g / L, the amount of nitrifying bacteria added is 0.5-1 g / L, the amount of denitrifying bacteria added is 0.5-1 g / L, and the amount of dissolved oxygen added is 0.1-2.5 mg / L.

[0013] Through the above scheme, this invention constructs a method for denitrification of marine aquaculture wastewater by the synergistic action of an iron-carbon micro-electrolysis system and a microbial denitrification system. In this method, both nitrifying and denitrifying bacteria can operate directly under micro-aerobic conditions, achieving simultaneous nitrification and denitrification within a single device or chamber.

[0014] In some preferred implementations, step (1) further includes adjusting the pH of the mariculture effluent to 7-8.5 before adding nitrifying bacteria, denitrifying bacteria, and iron-carbon packing material to the effluent.

[0015] Further preferred, the pH is 7.0-7.5.

[0016] In some preferred implementations, the amount of dissolved oxygen added is 1-2.5 mg / L.

[0017] In some preferred implementations, the reaction time for step (2) is 6-12 hours.

[0018] In some preferred embodiments, the addition amounts of nitrifying bacteria and denitrifying bacteria are 0.5 g / L, the addition amount of iron-carbon packing is 5 g / L, the pH is 7.5, the reaction time is 8 h, and the dissolved oxygen concentration is 1.5 mg / L.

[0019] In some preferred implementations, the nitrifying bacteria are GANDEW-NI and the denitrifying bacteria are GANDEW-DEN.

[0020] In some preferred implementations, the iron-carbon filler is a spherical particle with a diameter of 5-8 mm obtained by mixing activated carbon particles and reduced iron powder in a mass ratio of 1:4.

[0021] In some preferred implementations, the salinity of the seawater is 30‰.

[0022] In some preferred implementations, the pH of the seawater aquaculture tailwater is adjusted in step (1) by adding sodium hydroxide and / or dilute sulfuric acid.

[0023] In some preferred implementations, the solids in the mixture are removed by allowing it to stand until it separates into layers, then decanting and filtering while retaining the supernatant. Other possible implementations may employ solid-liquid separation methods commonly used by those skilled in the art, such as centrifugation or direct filtration.

[0024] The present invention has at least the following beneficial effects:

[0025] This invention combines an iron-carbon micro-electrolysis system and a microbial denitrification system to remove nitrogen from marine aquaculture wastewater. Under the optimized micro-aerobic conditions provided by this invention, the two systems work synergistically to improve the nitrogen removal rate. Compared to existing technologies that use both iron-carbon micro-electrolysis and microbial denitrification systems for denitrification, this invention achieves the same or even better nitrogen removal rates with less time and simpler reaction conditions. Attached Figure Description

[0026] Figure 1 A comparison chart of nitrogen removal rates at different pH levels;

[0027] Figure 2 A comparison chart of nitrogen removal rates at different reaction times;

[0028] Figure 3 A comparison chart showing the nitrogen removal rates under different amounts of nitrifying bacteria, denitrifying bacteria, and iron-carbon packing material;

[0029] Figure 4 A comparison chart of nitrogen removal rates under different dissolved oxygen addition amounts;

[0030] Figure 5 A comparison chart of the nitrogen removal rates of the denitrification method provided in this application with those of a separate iron-carbon microelectrolysis system and a microbial denitrification system under the same conditions. Detailed Implementation

[0031] This invention combines an iron-carbon micro-electrolysis system and a microbial denitrification system to denitrify seawater aquaculture wastewater. In the iron-carbon packing material, iron with a low potential acts as the anode, and carbon with a high potential acts as the cathode. The potential difference between the iron and carbon particles forms numerous micro-galvanic cells. The H2 adsorbed on the surface of the cathode carbon... + Alternatively, H₂O molecules accept electrons and are converted into adsorbed [H], then the adjacent adsorbed nitrate nitrogen is rapidly reduced to N₂ and ammonia nitrogen. Fe generated at the anode... 2+ The [H] and O· generated at the cathode have strong chemical activity, which can convert some recalcitrant organic pollutants such as antibiotics in marine aquaculture effluent into small-molecule organic matter, and provide additional carbon sources for heterotrophic denitrifying microorganisms, promoting efficient nitrogen removal. Under microaerobic conditions, the Fe produced by the anodic reaction... 2+ Further oxidation to Fe 3+ This process forms Fe(OH)3, a flocculant with high adsorption and flocculation activity, thereby achieving better pollutant removal. The numerous tiny galvanic cells formed during the iron-carbon micro-electrolysis process, generated by the anodic reaction, produce a micro-electric field. Under microcurrent stimulation, the cell permeability and gene expression levels of microorganisms change. Iron-carbon electron transfer can effectively stimulate microbial growth and the activity of metabolic enzymes, further enhancing the biodegradation capacity of microorganisms. Furthermore, the large pore size of the iron-carbon micro-electrolysis packing provides a habitat for microorganisms, promoting their growth, enhancing their resistance to shocks, and responding to changes in the quality of marine aquaculture tailwater at different stages of aquaculture. This influences the distribution of the microbial community and is beneficial for improving the removal rate of nitrogenous pollutants in marine aquaculture tailwater.

[0032] It should be noted that the amount of each component added in this invention refers to the concentration after it has been added to the system.

[0033] In the following embodiments, the water used may be one or more of distilled water, purified water, and drinking water; unless otherwise specified, the detection methods in the following embodiments are conventional detection methods; unless otherwise specified, the reagents in the following embodiments were purchased from commercial channels.

[0034] In the following embodiments, the iron-carbon packing material was prepared by thoroughly mixing activated carbon particles and reduced iron powder at a mass ratio of 1:4 and forming spheres with a particle size of 5-8 mm. This mass ratio was the optimal mass ratio determined by the inventors during the preliminary experimental stage. The microorganisms used were nitrifying bacteria and denitrifying bacteria, both in powder form, purchased from Shanghai Gandu Environmental Engineering Co., Ltd., China. The nitrifying bacteria strain was product model GANDEW-NI, and the denitrifying bacteria strain was product model GANDEW-DEN. The salinity of the seawater aquaculture tailwater was 30‰, and the pH was adjusted using a 2wt% dilute sulfuric acid and 2wt% sodium hydroxide solution.

[0035] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0036] Example 1

[0037] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0038] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0039] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0040] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0041] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0042] Example 2

[0043] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0044] (1) Adjust the pH of the effluent from seawater aquaculture to 7, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well and obtain the reaction solution;

[0045] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0046] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0047] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0048] Example 3

[0049] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0050] (1) Adjust the pH of the effluent from seawater aquaculture to 8, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well and obtain the reaction solution;

[0051] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0052] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0053] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0054] Example 4

[0055] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0056] (1) Adjust the pH of the effluent from seawater aquaculture to 8.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0057] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0058] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0059] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0060] Example 5

[0061] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0062] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0063] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 12 hours to obtain a mixed solution.

[0064] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0065] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0066] Example 6

[0067] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0068] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0069] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0070] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0071] The amount of iron-carbon filler added is 10 g / L, the amount of nitrifying bacteria added is 0.5 g / L, the amount of denitrifying bacteria added is 0.5 g / L, and the amount of dissolved oxygen added is 1.5 mg / L.

[0072] Example 7

[0073] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0074] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0075] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0076] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0077] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 1 g / L, the addition amount of denitrifying bacteria is 1 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0078] Example 8

[0079] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0080] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0081] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0082] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0083] The amount of iron-carbon filler added is 10 g / L, the amount of nitrifying bacteria added is 1 g / L, the amount of denitrifying bacteria added is 1 g / L, and the amount of dissolved oxygen added is 1.5 mg / L.

[0084] Example 9

[0085] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0086] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0087] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0088] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0089] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 0.1 mg / L.

[0090] Example 10

[0091] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0092] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0093] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0094] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0095] The amount of iron-carbon filler added is 5 g / L, the amount of nitrifying bacteria added is 0.5 g / L, the amount of denitrifying bacteria added is 0.5 g / L, and the amount of dissolved oxygen added is 0.5 mg / L.

[0096] Example 11

[0097] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0098] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0099] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0100] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0101] The amount of iron-carbon filler added is 5 g / L, the amount of nitrifying bacteria added is 0.5 g / L, the amount of denitrifying bacteria added is 0.5 g / L, and the amount of dissolved oxygen added is 1.0 mg / L.

[0102] Example 12

[0103] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0104] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0105] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 8 hours to obtain a mixed solution.

[0106] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0107] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 2.5 mg / L.

[0108] Comparative Example 1

[0109] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0110] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0111] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 2 hours to obtain a mixed solution.

[0112] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0113] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0114] Comparative Example 2

[0115] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0116] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0117] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 4 hours to obtain a mixed solution.

[0118] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0119] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0120] Comparative Example 3

[0121] A method for denitrifying marine aquaculture wastewater under microaerobic conditions includes the following steps:

[0122] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria, denitrifying bacteria and iron-carbon filler, mix well, and obtain the reaction solution;

[0123] (2) Dissolved oxygen was introduced into the reaction solution and the reaction was carried out for 24 hours to obtain a mixed solution.

[0124] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0125] The addition amount of iron-carbon filler is 5 g / L, the addition amount of nitrifying bacteria is 0.5 g / L, the addition amount of denitrifying bacteria is 0.5 g / L, and the addition amount of dissolved oxygen is 1.5 mg / L.

[0126] Comparative Example 4

[0127] A method for denitrification of marine aquaculture effluent treated by a single microbial system under microaerobic conditions includes the following steps:

[0128] (1) Adjust the pH of the effluent from seawater aquaculture to 7.5, then add nitrifying bacteria and denitrifying bacteria, mix well, and obtain the reaction solution;

[0129] (2) After introducing 0.1 mg / L of dissolved oxygen into the reaction solution, the reaction was carried out for 8 hours to obtain a mixed solution;

[0130] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0131] The addition amount of nitrifying bacteria was 0.5 g / L, the addition amount of denitrifying bacteria was 0.5 g / L, and the addition amount of dissolved oxygen was 1.5 mg / L.

[0132] Comparative Example 5

[0133] A method for denitrification of seawater aquaculture effluent treated by a standalone iron-carbon microelectrolysis system under microaerobic conditions includes the following steps:

[0134] (1) Adjust the pH of the effluent from the seawater aquaculture to 7.5, then add iron-carbon filler, mix well, and obtain the reaction solution;

[0135] (2) After introducing 0.1 mg / L of dissolved oxygen into the reaction solution, the reaction was carried out for 8 hours to obtain a mixed solution;

[0136] (3) Let the mixture stand until it separates into layers, then pour it out for filtration and retain the supernatant to obtain denitrified seawater aquaculture tailwater;

[0137] The amount of iron-carbon filler added is 5 g / L, and the amount of dissolved oxygen added is 1.5 mg / L.

[0138] Performance testing

[0139] The total nitrogen removal rate, ammonia nitrogen removal rate, nitrate nitrogen removal rate, and nitrite nitrogen removal rate of Examples 1-12 and Comparative Examples 1-5 were tested respectively. The methods for determining total nitrogen were alkaline potassium persulfate digestion ultraviolet spectrophotometry, ammonia nitrogen was determined by Nessler's reagent spectrophotometry, nitrate nitrogen was determined by ultraviolet spectrophotometry, and nitrite nitrogen was determined by N-(1-naphthyl)-ethylenediamine spectrophotometry. The results are as follows: Figures 1-5 As shown.

[0140] like Figure 1As shown, Examples 1-4 investigated the effect of pH on nitrogen removal rate. It can be seen that the removal rates of total nitrogen, ammonia nitrogen, nitrate nitrogen, and nitrite nitrogen all reached their optimal levels at pH = 7.5, followed by pH = 7.0. Furthermore, within the pH range of 7.5-8.5, the removal rates of each component gradually decreased with increasing pH. This may be because the iron-carbon micro-electrolysis system composed of iron-carbon packing material exhibits good nitrogen removal rates under acidic to neutral conditions, while nitrifying and denitrifying bacteria require a more moderate pH (approximately 7-8) to maintain high activity. At pH = 7.5, the synergistic effect of both achieves the highest removal rate. In addition, pH = 7-8.5 can meet the first-level discharge standards for marine aquaculture wastewater in Fujian and other regions, eliminating the need for pH adjustment after denitrification.

[0141] like Figure 2 As shown, Examples 1 and 5, as well as Comparative Examples 1-3, investigated the effect of reaction time on nitrogen removal rate. It can be seen that within 2-8 hours, the removal rates gradually increase with increasing reaction time, but decrease gradually after 8 hours. Therefore, setting the reaction time between 6-12 hours can ensure a high nitrogen removal rate.

[0142] like Figure 3 As shown, Examples 1 and 6-8 investigated the effects of the addition amount of iron-carbon packing material, nitrifying bacteria and denitrifying bacteria on nitrogen removal rate. It can be seen that the system has the highest removal rate when the addition amount of iron-carbon packing material is 5 g / L and the addition amount of nitrifying bacteria and denitrifying bacteria is 1 g / L.

[0143] The amount of dissolved oxygen added determines the activity of nitrifying and denitrifying bacteria. Meanwhile, under micro-aerobic conditions, the Fe produced by the anodic reaction... 2+ Further oxidation to Fe 3+ This forms Fe(OH)3, a flocculant with high adsorption and flocculation activity, thereby achieving better pollutant removal. For example... Figure 4 As shown, Examples 1 and 9-12 investigated the effect of dissolved oxygen (DO) addition on nitrogen removal rate. It can be seen that when the dissolved oxygen addition is between 0.1-2.5 mg / L, the removal rates for all parameters can reach over 60%. Specifically, when the dissolved oxygen addition is between 0.1-1.5 mg / L, the removal rate increases with increasing addition, while when the addition is 2.5 mg / L, the removal rates for all parameters are lower than in Example 1. In summary, when the dissolved oxygen addition is 1.5 mg / L, the iron-carbon packing material, nitrifying bacteria, and denitrifying bacteria can synergistically achieve the best nitrogen removal effect.

[0144] Figure 5By comparing the effects of synergistic denitrification using the microbial system and the iron-carbon microelectrode system, as well as denitrification using either system alone, in Examples 1, 4, and 5, it can be seen that the ammonia nitrogen removal rate of both the microbial system and the iron-carbon microelectrolysis system is less than 50%, the highest removal rate of nitrite nitrogen and nitrate nitrogen is only 72.38%, and the total nitrogen removal rate is less than 40%. In contrast, Example 1, under the same conditions, achieved a 100% removal rate for ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen, and a total nitrogen removal rate of 78.13%, which is greater than the sum of the total nitrogen removal rates of the microbial system and the iron-carbon microelectrolysis system.

[0145] The above description is merely a preferred embodiment of the present invention, and therefore should not be construed as limiting the scope of the present invention. All equivalent changes and modifications made in accordance with the scope of the patent and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for denitrification of mariculture effluent under microaerobic conditions, characterized by, The method comprises the following steps: (1) adjusting the pH of mariculture tail water to 7-8.5, then adding nitrifying bacteria GANDEWNI, denitrifying bacteria GANDEW-DEN and iron-carbon filler into the mariculture tail water, mixing to obtain a reaction liquid; (2) introducing dissolved oxygen into the reaction liquid to perform reaction, the reaction time is 2-24h, to obtain a mixed liquid; (3) removing the solid in the mixed liquid to obtain denitrified mariculture tail water; wherein the addition amount of the iron-carbon filler is 5-10g / L, the addition amount of the nitrifying bacteria is 0.5-1g / L, the addition amount of the denitrifying bacteria is 0.5-1g / L, and the addition amount of the dissolved oxygen is 0.1-2.5mg / L.

2. The denitrification method as claimed in claim 1, characterized in that, The pH is 7.0-7.

5.

3. The denitrification method as claimed in claim 1, characterized in that, The addition amount of the dissolved oxygen is 1-2.5mg / L.

4. The denitrification method as claimed in claim 1, characterized by, The reaction time of step (2) is 6-12h.

5. The denitrating method as claimed in claim 1, characterized by, The addition amount of the nitrifying bacteria and the denitrifying bacteria is 0.5g / L respectively, the addition amount of the iron-carbon filler is 5g / L, the pH is 7.5, the reaction time is 8h, and the concentration of the dissolved oxygen is 1.5mg / L.

6. The denitrification method according to any one of claims 1 to 5, characterized by, The iron-carbon filler is a round ball with a particle size of 5-8mm, which is obtained by mixing activated carbon particles and reduced iron powder with a mass ratio of 1:

4.

7. The denitrating method as claimed in claim 1, characterized by, The salinity of the seawater is 30‰.

8. The denitrating method as claimed in claim 1, characterized by, The pH of the mariculture tail water in step (1) is adjusted by adding sodium hydroxide and / or dilute sulfuric acid.

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