Nitrite poisoning has always been a tough problem encountered in the breeding process, and now seven free methods for degrading nitrite are published free of charge. I hope to bring some inspiration to the farmers. In recent years, farming practice has proved that nitrite poisoning has always been a difficult problem encountered in the breeding process, and often brings relatively heavy losses to the farmers. There are currently no specific drugs that can degrade nitrite, but in practice, various measures can be taken to alleviate and reduce the harm caused by nitrite. Although there are many measures, how to make reasonable and flexible choices makes many fish disease prevention workers and farmers suffer. The author summarizes and summarizes the current control methods and effects of nitrite in culture, for everyone.  

First, direct degradation method  

1, oxidation method  

The nitrogen in the nitrite ion is in the intermediate valence state and has an oxidized property. When NO2- in the medium encounters an oxidant, it will change the valence state of nitrogen, and will be oxidized by the change of the gain and loss electrons. Finally, the NO2-ion will be converted into a less toxic or even non-toxic substance. There are many substances having the ability to oxidize nitrite ions, such as ozone, hydrogen peroxide, sodium hypochlorite, etc., but only suitable for use in aquaculture water, such as trichloroisocyanuric acid, dichloroisocyanuric acid, bromochlorohydantoin, Several strong oxidizing disinfectants such as chlorine dioxide.  

The advantage of using a strong oxidizing agent to oxidize NO2- ions to become NO3- ions is that the reaction rate is fast, the cost is low, and the oxidation efficiency is high. However, this method is rarely used in actual production to degrade nitrite. The main reason is that the degradation rate of nitrite is low in these strong oxidizing disinfectants at normal use concentration (the effect of degrading nitrite at low concentration is not obvious). , high concentration will cause phytotoxicity), in addition to the oxidative degradation of nitrite, there are still weaknesses that tend to rebound. This method is preferred when the following conditions occur in production: 1 normal preventive disinfection, but the nitrite content is about 0.2 mg / liter, you can use granular trichloroisocyanuric acid (such as chlorhexidine, can directly reach The bottom of the pool, improve the quality of the substrate, control the formation of nitrite.) The whole pool is thrown, which not only prevents fish disease but also controls nitrite. 2 The outbreak of fish disease requires disinfection. When the nitrite content is about 0.2 mg/L, priority is given. The use of binary chlorine dioxide not only kills pathogens, but also improves the environment and shortens recovery time.  

2, reduction method  

In recent years, some experts have used NO2- to reduce the oxidizing property under acidic conditions and to reduce the NO2-degradation into a volatile gas and automatically get rid of the reaction system. For example, Zhang Xiuyun found that the cast iron chips had a certain removal effect on NO2-, and the removal effect increased with the increase of the amount of cast iron. According to the standard oxidation-reduction potential, Fe can convert nitrite into N2 or ammonia nitrogen under weakly acidic conditions. Xue Li et al. treated the wastewater containing sodium nitrite for 1 h at 100 ° C by ammonium salt method. The NO2- content reaches the emission standard. The basic principle of the method is: NH4++ NO2-→NH4NO2→N2↑+H2O. There are many similar studies, but these chemical reactions are conditional and are only suitable for industrial water treatment. Through the efforts of the researchers of aquatic products, we have found a safe and economical reducing agent suitable for aquaculture water use - nitrite degradation agent (for the benefit of the enterprise, the author is inconvenient to disclose), and processed by advanced formulation technology Multiple dosage forms are marketed.  

The nitrite degradation agent raw material has a low cost, about 4,000 yuan / ton, which is suitable for production by a fishery medicine enterprise, and therefore has a high occupation rate in the sub-products. This kind of product has the following advantages in use: 1 rapid degradation, from sprinkling into water body to the end of reaction, only about 5 hours, especially suitable for shrimp nitrite poisoning first aid; 2 safe and environmentally friendly, the drug is simple in structure, in water body and The nitrite is rapidly degraded after the reaction, and has no toxic side effects on the cultured animals, and will not cause secondary pollution of the aquaculture water. It is worth noting that the agent can be used in rainy days; 3 completely denitrification, the drug will directly nitrite nitrogen It is reduced to nitrogen and volatilized into the air, and the nitrate ion formed by the oxidation method may be refluxed into nitrite under the action of denitrifying bacteria; 4 the degradation rate is high, and the highest can reach more than 90%, which is unmatched by other methods. The same weakness is observed between the reduction method and the oxidation method, that is, the maintenance time is short, and the water nitrite is likely to rebound.  

3. Physical adsorption method  

The physical adsorption method uses a substance having high adsorption capacity, such as zeolite powder, silica gel, activated carbon, sepiolite, etc., to adsorb nitrite in its structure. This method is widely used in production, and many of the bottom modification products contain adsorbent components. The advantage is that the action time is short and the cost is low. The disadvantage is that the dosage is large, such as zeolite powder, 50-100 kg/mu.  

4, fertilizer water method  

Nitrite is rich in nitrogen fertilizer and is the basic nutrient for algae growth and reproduction. Therefore, speeding up the growth and reproduction of water algae can effectively reduce the concentration of nitrite. Production practices are achieved using single-cell plant growth regulators (sodium nitrophenolate, biochemical fulvic acid, sodium humate, amino acids, etc.), photosynthesis catalysts, trace elements, and silicon fertilizers. It is worth noting that when the water body nitrite is high, it indicates that the nitrogen fertilizer is sufficient. Do not use nitrogen fertilizer to increase the nitrogen circulation burden of the water body. Phosphate fertilizer can be applied to achieve the purpose of “phosphorus-promoting nitrogen”.

Degradation of nitrite by fertilizer method is worthy of promotion in modern ecological breeding, but it is subject to the following conditions: 1 The transparency of water body is required to be greater than 30 cm. If it is due to low transparency caused by organic matter and debris, it should be splashed with flocculating purifying agent; The weather is fine in five days, the temperature is suitable for algae reproduction; 3 the nitrite concentration below 0.4 mg/L is not affected by the cultured animals; 4 the algae phase is uniform, if the harmful algae prevails, the water should be changed first. Measures such as excellent algae; 5 pairs of water samples, if there are too many zooplankton, splash pesticides first. For example, in areas where the rotifer hazard is more serious, it is difficult to treat nitrite without taking the rotifer first.

5, bacterial decomposition method

At present, we know two types of bacteria: nitrifying bacteria and denitrifying bacteria. Nitrifying bacteria can convert nitrite into nitrate, which needs to be carried out under aerobic conditions; denitrifying bacteria reduce nitrite to under anoxic conditions. N2 or nitroxides.

Many of the sub-products on the market are marked with the main components of nitrifying bacteria and denitrifying bacteria, but they have not shown the desired effect in practice, and can only be said to play a preventive and mitigating role. In theory, nitrifying bacteria and denitrifying bacteria can reduce nitrite, but because they are autotrophic bacteria, the growth and reproduction rate is slow, it takes more than 20 hours to breed, plus the preservation technology and application of fungi. After the water body survival rate, water environment and other aspects, the degradation of nitrite by nitrifying bacteria and denitrifying bacteria is not ideal. More importantly, denitrification is more likely to occur if the dissolved oxygen in the pond is insufficient. Denitrification may reduce the nitrate to nitrite, which in turn causes the nitrite to rise for a certain period of time, so be careful.

Recent studies have shown that the reduction of nitrate to nitrite is carried out by dissimilatory nitrate reductase. The author has successfully developed a dissimilatory nitrate reductase passivator, which has an obligatory nature and does not affect the biochemical enzyme activities of other microorganisms. Tests have shown that after the application of this passivating agent in the pond, the growth rate and nitrification rate of nitrifying bacteria are increased, and the nitrite is controlled within a safe concentration range within 30-40 days. The drug is almost unaffected by the water environment and is expected to completely solve the worldwide problem of nitrite plaguing the aquaculture industry. Related tests are still being further refined.

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