Denitrification method for mariculture tail water under micro-aerobic condition

Abstract

The invention discloses a denitrification method for mariculture tail water under a micro-aerobic condition, an iron-carbon micro-electrolysis system and a microbial denitrification system are combined to jointly perform denitrification on the mariculture tail water, and under the optimized micro-aerobic condition provided by the invention, the iron-carbon micro-electrolysis system and the microbial denitrification system generate a synergistic effect, so that the removal rate of nitrogen is increased. Compared with the prior art in which an iron-carbon micro-electrolysis system and a microbial denitrification system jointly carry out denitrification, the method has the advantage that the same or even better nitrogen removal rate can be achieved only by short time and simple reaction conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a method for denitrifying seawater aquaculture tail water under microaerobic conditions. Background Art

[0002] In recent years, China has made remarkable progress in aquaculture. In 2022, the output value of aquaculture in my country was 1,250.187 billion yuan, a year-on-year increase of 6.2%; the area of ​​marine aquaculture was 2,074.42 thousand hectares, a year-on-year increase of 2.4%; the output of marine aquaculture products was 22.757 million tons, a year-on-year increase of 2.9%. With the rapid expansion of high-yield and high-density aquaculture, marine aquaculture activities produce harmful substances due to the decay and decomposition of residual feed and excrement, leading to water quality deterioration, endangering the health of aquatic organisms, and seriously hindering the sustainable development of marine aquaculture activities. Therefore, the treatment of marine aquaculture tailwater and the development of marine aquaculture tailwater treatment technology have become urgent research topics 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 late stages of high-density aquaculture, the maximum amount of feed addition needs to be met. A large amount of nitrogen remains in the aquaculture water along with leftover bait and feces. Nitrogen gradually accumulates, and the C / N ratio decreases with the process of aquaculture production. Therefore, marine aquaculture effluent has the characteristic of a low C / N ratio.

[0004] Biological treatment technology is a technology with a wide range of applications, stable effects and high safety. Its principle is mainly to put organisms with certain cleaning ability into the tail water of aquaculture for water purification. Although biological treatment is widely used in water treatment due to its high efficiency and economic feasibility. However, even well-adapted microorganisms can only treat relatively low concentrations of pollutants, and high concentrations of chemicals will inhibit the growth and reproduction of microorganisms. Therefore, microorganisms alone have limited effects on the removal of nitrogen-containing pollutants in marine aquaculture tail water. The removal rate of ammonia nitrogen is 49.52%, the removal rate of nitrate nitrogen is 66.21%, and the removal rate of nitrite nitrogen is 68.40%, but the maximum total nitrogen removal rate is only 37.69%, which needs to be further improved. In addition, the denitrification performance of traditional biological treatment technology is affected by whether there is oxygen in the reaction environment. Denitrification consists of two processes: nitrification and denitrification. Nitrification reaction refers to the process of oxidizing ammonia nitrogen to nitrate nitrogen by nitrifying bacteria under aerobic conditions, and denitrification reaction refers to the process of reducing nitrite and nitrate to gaseous nitrogen by denitrifying bacteria under anoxic conditions. In this context, further exploration is still needed to promote traditional microbial denitrification and efficiently achieve simultaneous nitrification and denitrification.

[0005] CN112047456A proposes a microbial fuel cell wastewater denitrification device and method, which separates the device into a micro cathode chamber and an anode chamber, and the cathode chamber is filled with biological ceramsite filler and iron-carbon micro-electrolysis filler, and the cathode is alternately fed with air and carbon dioxide to alternate between anaerobic and aerobic conditions, and then nitrification and denitrification are carried out in the cathode. The ammonia nitrogen removal rate of the device reaches 69.4-90.7%, and the total nitrogen removal rate reaches 59.2-80.1%. Compared with the traditional microbial denitrification method, it has achieved a better denitrification effect, but it needs to separate the device into two chambers and intermittently aerate the cathode chamber. The device and operation are relatively complex, and multiple materials need to be coordinated and the required reaction time is more than 24 hours, which still needs to be further optimized. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and provide a method for denitrifying marine aquaculture tail water under microaerobic conditions.

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

[0008] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0009] (1) adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler to seawater aquaculture tail water, mixing them evenly, and obtaining a reaction solution;

[0010] (2) introducing dissolved oxygen into the reaction solution and reacting for 2-24 hours to obtain a mixed solution;

[0011] (3) removing solids from the mixed solution to obtain denitrified marine aquaculture tail water;

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

[0013] Through the above scheme, the present invention constructs a denitrification method for seawater aquaculture tail water by the synergistic action of the iron-carbon micro-electrolysis system and the microbial denitrification system, wherein both nitrifying bacteria and denitrifying bacteria can work directly under microaerobic conditions, achieving simultaneous nitrification-denitrification in one device or chamber.

[0014] In some preferred implementations, step (1) further comprises, before adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler to the seawater aquaculture tail water, adjusting the pH of the seawater aquaculture tail water to 7-8.5.

[0015] More preferably, 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 of step (2) is 6-12 hours.

[0018] In some preferred implementations, the addition amount of nitrifying bacteria and denitrifying bacteria is 0.5 g / L respectively, the addition amount of iron-carbon filler is 5 g / L, the pH is 7.5, the reaction time is 8 h, and the concentration of dissolved oxygen 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 sphere with a particle size 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 seawater is 30‰.

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

[0023] In some preferred implementations, the solids in the mixed solution are removed by standing the mixed solution until the mixed solution is separated into layers, then filtering by decantation and retaining the supernatant. In other possible implementations, solid-liquid separation methods commonly used by those skilled in the art, such as centrifugal separation and direct filtration, may also be used.

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

[0025] The present invention combines the iron-carbon micro-electrolysis system and the microbial denitrification system to denitrify the tail water of marine aquaculture. Under the optimized microaerobic conditions provided by the present invention, the two produce a synergistic effect to improve the nitrogen removal rate. Compared with the existing technology of denitrification by the iron-carbon micro-electrolysis system and the microbial denitrification system, it only takes a shorter time and simpler reaction conditions to achieve the same or even better nitrogen removal rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a comparison chart of nitrogen removal rate at different pH;

[0027] Figure 2 It is a comparison chart of nitrogen removal rate under different reaction times;

[0028] Figure 3 The figure is a comparison of nitrogen removal rates under different addition amounts of nitrifying bacteria, denitrifying bacteria and iron-carbon fillers;

[0029] Figure 4 This is a comparison chart of nitrogen removal rates under different amounts of dissolved oxygen added;

[0030] Figure 5 A comparison chart of the nitrogen removal rate of the denitrification method provided in this application and the separate iron-carbon micro-electrolysis system and microbial denitrification system under the same conditions. DETAILED DESCRIPTION

[0031] The present invention combines the iron-carbon micro-electrolysis system and the microbial denitrification system to denitrify the tail water of seawater aquaculture. The iron with low potential in the iron-carbon filler is used as the anode, and the carbon with high potential is used as the cathode. There is a potential difference between the iron-carbon particles to form a large number of tiny primary cells. The H adsorbed on the surface of the cathode carbon + Or H2O molecules accept electrons and are converted into adsorbed [H], and then the adjacent adsorbed nitrate nitrogen is quickly reduced to N2 and ammonia nitrogen. 2+ The [H] and O· generated at the cathode have strong chemical activity and can convert some difficult-to-degrade organic pollutants such as antibiotics in marine aquaculture tail water into small molecular organic matter, and provide additional carbon sources for heterotrophic denitrifying microorganisms, promoting efficient denitrification. Under microaerobic conditions, the Fe 2+ Further oxidized to Fe 3+ , forming a flocculant Fe(OH)3 with high adsorption and flocculation activity, thereby achieving better pollutant removal effect. The large number of tiny primary cells formed in the iron-carbon micro-electrolysis process produced by the anode reaction generate a micro-electric field. Under the stimulation of microcurrent, the cell permeability and gene expression levels of the microorganisms change. Iron-carbon electron transfer can effectively stimulate the growth of microorganisms and the activity of metabolic enzymes, and further improve the biodegradation ability of microorganisms. In addition, the large pore size of iron-carbon micro-electrolysis fillers can provide a habitat for microorganisms, promote microbial growth, enhance microbial impact resistance, respond to changes in seawater aquaculture tail water quality at different aquaculture periods, affect the distribution of microbial communities, and help improve the removal rate of nitrogen-containing pollutants in seawater aquaculture tail water.

[0032] It should be noted that the addition amount of each component in the present invention refers to the concentration after adding it into the system.

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

[0034] In the following examples, the iron-carbon filler is made of activated carbon particles and reducing iron powder in a mass ratio of 1:4, and then completely mixed to form a sphere with a particle size of 5-8 mm. This mass ratio is the best mass ratio measured by the inventor in the preliminary experiment stage. The microorganisms used are nitrifying bacteria and denitrifying bacteria, both in powder form, purchased from Shanghai Gandu Environmental Engineering Co., Ltd., China. The product model of the nitrifying bacteria species is GANDEW-NI, and the product model of the denitrifying bacteria species is GANDEW-DEN. The salinity of the seawater aquaculture tail water is 30‰, and the pH is adjusted using 2wt% dilute sulfuric acid and 2wt% sodium hydroxide solution.

[0035] The technical solution of the present invention is further illustrated and described below through specific implementation methods.

[0036] Example 1

[0037] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0038] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0039] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0040] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0042] Example 2

[0043] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0044] (1) adjusting the pH of seawater aquaculture tail water to 7, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0045] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0046] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0048] Example 3

[0049] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0050] (1) adjusting the pH of seawater aquaculture tail water to 8, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing to obtain a reaction solution;

[0051] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0052] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0054] Example 4

[0055] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0056] (1) adjusting the pH of seawater aquaculture tail water to 8.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0057] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0058] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0060] Example 5

[0061] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0062] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0063] (2) introducing dissolved oxygen into the reaction solution and reacting for 12 h to obtain a mixed solution;

[0064] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0066] Example 6

[0067] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0068] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0069] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0070] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0072] Example 7

[0073] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0074] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0075] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0076] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0078] Example 8

[0079] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0080] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0081] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0082] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0084] Example 9

[0085] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0086] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0087] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0088] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0090] Example 10

[0091] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0092] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0093] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0094] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0096] Embodiment 11

[0097] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0098] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0099] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0100] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0102] Example 12

[0103] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0104] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0105] (2) introducing dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0106] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0108] Comparative Example 1

[0109] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0110] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0111] (2) introducing dissolved oxygen into the reaction solution and reacting for 2 h to obtain a mixed solution;

[0112] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0114] Comparative Example 2

[0115] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0116] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0117] (2) introducing dissolved oxygen into the reaction solution and reacting for 4 h to obtain a mixed solution;

[0118] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0120] Comparative Example 3

[0121] A method for denitrifying marine aquaculture tail water under microaerobic conditions comprises the following steps:

[0122] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler, and mixing well to obtain a reaction solution;

[0123] (2) introducing dissolved oxygen into the reaction solution and reacting for 24 hours to obtain a mixed solution;

[0124] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0126] Comparative Example 4

[0127] A method for denitrifying marine aquaculture tail water treated by a single microbial system under microaerobic conditions comprises the following steps:

[0128] (1) adjusting the pH of seawater aquaculture tail water to 7.5, then adding nitrifying bacteria and denitrifying bacteria, and mixing them to obtain a reaction solution;

[0129] (2) introducing 0.1 mg / L dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0130] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

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

[0132] Comparative Example 5

[0133] A method for denitrifying seawater aquaculture tail water treated by a single iron-carbon micro-electrolysis system under microaerobic conditions comprises the following steps:

[0134] (1) adjusting the pH of the marine aquaculture tail water to 7.5, then adding the iron-carbon filler and mixing well to obtain a reaction solution;

[0135] (2) introducing 0.1 mg / L dissolved oxygen into the reaction solution and reacting for 8 h to obtain a mixed solution;

[0136] (3) allowing the mixed solution to stand until stratification, then filtering by decantation and retaining the supernatant to obtain denitrified marine aquaculture tail water;

[0137] Among them, the added amount of iron-carbon filler is 5g / L, and the added amount of dissolved oxygen is 1.5mg / 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 total nitrogen determination method was alkaline potassium persulfate digestion ultraviolet spectrophotometry, the ammonia nitrogen determination method was Nessler's reagent spectrophotometry, the nitrate nitrogen determination method was ultraviolet spectrophotometry, and the nitrite nitrogen determination method was N-(1-naphthyl)-ethylenediamine spectrophotometry. The results are as follows: Figure 1-Figure 5 shown.

[0140] like Figure 1As shown, Examples 1-4 explored the effect of pH on the removal rate of nitrogen. It can be seen that at pH = 7.5, the removal rates of total nitrogen, ammonia nitrogen, nitrate nitrogen and nitrite nitrogen all reached the optimal level, followed by pH = 7.0. And in the range of pH = 7.5-8.5, as the pH increases, the removal rates of each item gradually decrease. This may be because the iron-carbon micro-electrolysis system composed of iron-carbon fillers has a good removal rate for nitrogen under acidic to neutral conditions, while nitrifying bacteria and denitrifying bacteria need to have higher activity at a milder pH (about 7-8). When pH = 7.5, the synergistic effect of the two achieves the highest removal rate. In addition, pH = 7-8.5 can also meet the primary discharge standards for marine aquaculture tail water in Fujian and other places, without the need to adjust the pH after denitrification.

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

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

[0143] The amount of dissolved oxygen added determines the activity of nitrifying and denitrifying bacteria. At the same time, under microaerobic conditions, the Fe 2+ Further oxidized to Fe 3+ , forming a flocculant Fe(OH)3 with higher adsorption and flocculation activity, thereby achieving better pollutant removal effect. Figure 4 As shown, Example 1 and Examples 9-12 explored the effect of the amount of dissolved oxygen (DO) added on the nitrogen removal rate. It can be seen that when the amount of dissolved oxygen added is between 0.1-2.5 mg / L, the removal rates of each item can reach more than 60%. Among them, when the amount of dissolved oxygen added is between 0.1-1.5 mg / L, the removal rate increases with the increase of the amount added, and when the amount added is 2.5 mg / L, the removal rates of each item are lower than that of Example 1. In summary, when the amount of dissolved oxygen added is 1.5 mg / L, iron-carbon filler, nitrifying bacteria and denitrifying bacteria can synergistically achieve the best denitrification effect.

[0144] Figure 5By comparing the effects of the microbial system and the iron-carbon microelectrode system in synergistic denitrification and the denitrification of the two separately through Example 1, Comparative Example 4 and Comparative Example 5, it can be seen that the ammonia nitrogen removal rate of the microbial system and the iron-carbon microelectrolysis system is less than 50%, the removal rate of nitrite nitrogen and nitrate nitrogen is only 72.38% at most, and the total nitrogen removal rate is less than 40%. Under the same conditions, the removal rates of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in Example 1 all reached 100%, and the total nitrogen removal rate was 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 only a preferred embodiment of the present invention, and therefore cannot be used to limit the scope of the present invention. That is, equivalent changes and modifications made according to the patent scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for denitrification of marine aquaculture tail water under microaerobic conditions, characterized in that: The steps include: (1) adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler to seawater aquaculture tail water, mixing them evenly, and obtaining a reaction solution; (2) introducing dissolved oxygen into the reaction solution and reacting for a reaction time of 2-24 hours to obtain a mixed solution; (3) removing solids from the mixed solution to obtain denitrified marine aquaculture tail water; Among them, 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 according to claim 1, characterized in that: Step (1) also includes adjusting the pH of the seawater aquaculture tail water to 7-8.5 before adding nitrifying bacteria, denitrifying bacteria and iron-carbon filler to the seawater aquaculture tail water.

3. The denitrification method according to claim 2, characterized in that: The pH is 7.0-7.

5.

4. The denitrification method according to claim 1, characterized in that: The added amount of dissolved oxygen is 1-2.5 mg / L.

5. The denitrification method according to claim 1, characterized in that: The reaction time of step (2) is 6-12h.

6. The denitrification method according to claim 1, characterized in that: The addition amount of the nitrifying bacteria and the denitrifying bacteria is 0.5 g / L respectively, the addition amount of the iron-carbon filler is 5 g / L, the pH is 7.5, the reaction time is 8 hours, and the concentration of dissolved oxygen is 1.5 mg / L.

7. The denitrification method according to any one of claims 1 to 6, characterized in that: The nitrifying bacteria is GANDEW-NI, and the denitrifying bacteria is GANDEW-DEN.

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

4.

9. The denitrification method according to claim 1, characterized in that: The salinity of the seawater is 30‰.

10. The denitrification method according to claim 2, characterized in that: In step (1), the pH of the seawater aquaculture tail water is adjusted by adding sodium hydroxide and / or dilute sulfuric acid.

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