With the rapid development of China's aquaculture industry, various advanced water treatment technologies have been widely applied, such as sand filtration, microbial purification, ultraviolet disinfection, and foam separation. However, with the application of industrialized closed recirculating aquaculture equipment in actual production, the production conditions for high density and small water bodies are more stringent for water quality. Therefore, the application of high-efficiency, rapid characteristics of ozone water treatment technology came into being. 1 Characteristics of ozone Ozone (O3), also known as active oxygen, is an isomer of oxygen. It is easily soluble in water and undergoes a reduction reaction in water. It produces monoatomic oxygen and hydroxyl (0H) monoatomic oxygen oxidation of intermediate materials. Very strong, hydroxyl is also a strong oxidant, catalyst, therefore, ozone has a strong disinfection effect, and can break down the organic oxidant is difficult to destroy the monoatomic oxygen and hydroxyl sterilizing mechanism: (1) ozone can break down the bacterial cell wall, Diffusion into human cells, oxidative destruction of enzymes in the cell to kill pathogens; (2) Ozone reacts with bacterial cell wall lipids, enters into the bacterial body, acts on lipoproteins and lipopolysaccharides, changes the cell's permeability Sex, which leads to cell lysis. The ability of ozone to disinfect and decompose organic matter and inorganic matter in water is several hundred times higher than that of commonly used chlorine. Moreover, due to the instability of ozone, oxygen and water are easily generated after the reaction, so that it will not cause secondary pollution. 2 Based on the strong oxidizing property of ozone, ozone can purify water, making it have a good killing effect on various microorganisms in water. Wu Xuezhou and others in the sterile hood (0.7m) open ozone, found that after 20min and 30min ozone effect E. coli killing rate of 97.5% and l00%; killing rate of Staphylococcus aureus was 937% and l00 %; The killing rate of Pseudomonas aeruginosa was 84.6% and 89.8%. Herbokd et al. reported that the ozone gas flowed through the water at 20Â°C, and when the ozone concentration in the water reached 0.43 mg/L, the large intestine could be reached. Bacillus 100% to kill the hairy forest, etc. reported at 34 Â°C 1 Â°C, the concentration of 5.50mg / m of ozone within 45min can be 100ml plastic bottle drops of Bacillus subtilis var. spp. The 1.5mg/L ozone solution can kill 100% of Aspergillus niger, yeast, and other fungi in only 1min. In addition, ozone can also kill the protozoa and their eggs. 3 Characteristics of ozone purification of water quality 3.1 Due to the strong oxidizing property of ozone, nitrites, hydrogen sulfide, and ammonia cyanide that are harmful to fish in freshwater or seawater for culture can be oxidized to non-toxic NO, SO, N, and other organic substances, as well as inorganic substances can also be degraded to produce non-toxic substances to the organism, thereby reducing the biological oxygen demand (BOD) and chemical oxygen demand (COD) in the water 3.2 The strong oxidizing power of ozone can be applied to algae Such as the original vivid plants to play a role in the rapid killing, according to Sun Xiaohong and other reports, take red tide seawater for 30min ozone treatment, the red red tide water completely oxidized into a colorless and transparent, all the water in the nocturnal insect was crushed. 3.3 Ozone can effectively kill Buffalo's biological health pathogens in water. Kofich et al. compared the killing effect of ozone, CIO, CI, and chloride nitrogen on Cryptosporidium parvum eggs. The results showed that lrng/kg of ozone for 5min can inactivate 90% of the cysts. With the same concentration of CIO, the same effect was achieved after the effects of 1h, CI, and chlorine-nitrogen at a concentration of 80mg/kg and 90rain. 3.4 Because ozone is easily decomposed into 0 in water, it can not only play the role of sterilization, but also can increase the oxygen of the water body, until the dual effect of 3.55 ozone does not change the water in the process of purifying water quality. Original ingredients. The minerals beneficial to aquatic animals contained in water can be maintained. 3.6 By purifying the water source by ozone, it can also reduce the number of bacteria that feed on the host's intestines to feed on the host's nutrition. Reduce the nutrient consumption of juvenile bacteria, increase the activity of amylase secreted by beneficial bacteria, increase the utilization of food nutrients by animals, and promote the healthy growth of animals. 3.7 Ozone will purify the water quality through oxidative flocculation, not Secondary pollutants are generated. The oxides produced during the sterilization process are non-toxic and odorless biodegradable substances. 4 Factors that affect the effect of ozone 4.1 The concentration of ozone Within the allowable concentration, the higher the concentration of ozone in general, the faster the speed of killing bacteria and the like, the better the effect, but care should be taken not to overdo it 4.2 The same ozone concentration of water at different temperatures will result in different amounts of dissolved water. The lower the water temperature, the higher the solubility in water, such as 30, the solubility of 22%, lO is 54%. 0cc is 69% 4.3 inorganic ions in water When there are more inorganic ions in the water, it will accelerate the decomposition of ozone, so that the concentration of ozone is reduced, impeding the efficiency of sterilization - 4.4 turbidity in water It was reported that when the water When the turbidity is less than 5 mg/L, the effect of ozone sterilization is not significant, but when the turbidity is more than 5 mg/L, it has an effect. Because at this time, a large part of the ozone is used for the oxidative decomposition of organic and inorganic substances. The toxic side effect of residual ozone in 5 water on aquatic organisms is shown by Jiang Guoliang et al. (2001) in the acute toxicity test of ozone on gingiva and shrimp. When the residual ozone concentration was 0.2-0.4 mg/LH~ after l2h, the gingiva survived 65%; at 24h it was 47%; at 48h it was 23%; when the concentration increased to 0.5~0.8ml/L No survival at any time, Reid. B (1994) studies showed that the ozone concentration of l-5mg/1 is the lethal concentration of shrimp. The Hubbs study found that the toxicity of fish in the presence of high residual ozone concentration is mainly due to abnormal movement and breathing, which leads to loss of balance. The fish often lags and rests. When the fish is still, the sides or belly of the fish face upward, eventually leading to the death of fish. Therefore, although ozone can significantly purify water quality and increase fish and shrimp production, its toxic effects on fish and shrimps and other aquatic organisms cannot be ignored. Practical applications should be based on actual conditions. The use of small doses (usually 0.05 ~ 0.3mg/L) and short-term (O.3 ~ 2min) contact in a summary, due to the advantages of ozone itself, such as a broad bactericidal spectrum. The effect is fast and thorough, no secondary pollution. It can decontaminate inorganic matter, organic matter, etc. to purify water and increase dissolved oxygen. Therefore, ozone is an ideal disinfectant, which can be widely used in the treatment of culture and domestic water, and ozone can significantly improve water quality. When circulating aquaculture systems, it can save a lot of water and reduce the thermal energy consumed for temperature control. Therefore, in the long run, the application of ozone for water quality treatment is an economical and effective water treatment method.
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