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In many high-yield areas of aquaculture, it is necessary to make the role of aerators and the contribution rate of production are very large, basically equipped with impeller aerators on the pool area of about 5 acres, even 1-2 acres, the climate is not good, 24 Open the aerator in 365 days, don't hesitate to pay for electricity costs, and ask for thousands of yen per mu. Except for the abundance of aquaculture technology and capital and marketing methods, aerator = a booster, this is the Increase production and increase efficiency. Of course, in some special cases, the increase in output does not improve efficiency, and the increase in output does not necessarily increase efficiency, but this is not much. In low-yield aquaculture areas, the obvious is the aerator, but here can only be a "life-saving machine", the fishermen are particularly painful in terms of electricity, waiting for the fish to float or die in the flooding pond, this is just Using aeration machines to "save lives", of course, how the production can not be improved, aeration machine lifesaving machines, of course, such results are not surprising. In my country's fishing water quality standards, it is stipulated that the dissolved oxygen content must be greater than 5 mg/L for more than 16 hours for 24 consecutive hours, and not less than 3 mg/L at any other time. However, in actual farming, the dissolved oxygen in the pond water is sometimes very low, which cannot meet the normal growth of fish and maintain basic metabolism, resulting in weak activity, poor feeding ability, slow growth, waste of bait and high bait coefficient, and cannot be decomposed well. Oxygen decomposes organic matter, poor water quality, and farmed fish are susceptible to diseases, and even low dissolved oxygen in the water, resulting in anoxic floating heads of farmed fish, resulting in the death of the entire farmed fish pond, causing significant losses.
1. Analyze the principle of aeration effect of aeration machine
In the adult fish pond, the impeller type aerator is ly used. It has the functions of aeration, water stirring and aeration. Although they are completed at the same time in the process of operation, under different circumstances, they mainly play one or two roles.
① Oxygen-increasing effect: Generally, oxygen can be added to water from 1.0 kg/kW·h to 1.5 kg/kW·h. When the water surface of the aerator is large (for example, 1.5 mu/kW·hour to 3.0 mu/kW·hour), the oxygenation value distributed evenly over the entire water body of the pond is not high. Therefore, for the large pond water body, the actual aeration effect is not obvious in the short term, only the water jump ring around the aerator maintains a high oxygen dissolution area, so that the fish cluster is within this range, and saving is achieved The purpose of fish. In order to exert the aeration effect of the aerator, the technology of predicting the floating head should be used, and it should be turned on before the fish floating head at night to prevent the dissolved oxygen in the pool water from further decreasing. In production, 2 mg/L dissolved oxygen can be used as a warning line for starting, and tilapia or wild fish floating head can be used as a biological indicator for starting. If the load water level of the aerator is small (for example, 0.8-1.2 mu/kW·h), the effect of aeration of the pool water is more obvious.
② Stirring effect: The agitator has a good stirring performance and the liquid level is updated quickly, so that the water temperature and dissolved oxygen of the pool water can be evenly distributed in a short period of time. The temperature difference and oxygen difference between the upper and lower water layers of the fish pond at noon on a clear day are large. At this time, the aerator can be fully used to stir the water. The smaller the load water surface of the aerator, the shorter the circulation time of the upper and lower water layers, and the dissolved oxygen in the upper and lower water layers of the entire fish pond is basically evenly distributed.
③ Aeration effect: When the aerator is in operation, the dissolved gas in the water will escape from the water surface through the water jump and the liquid level update. The rate of escape is proportional to the concentration of the gas in water. That is, the higher the concentration of a gas in water, the easier it is to escape into the air after switching on. Therefore, the escaping speed of harmful gas (such as hydrogen sulfide, ammonia, etc.) in the lower layer of water after startup is greatly accelerated, and at this time, an odor can be smelled in the oxygen engine. Turning on at noon also accelerates the escape rate of dissolved oxygen in the upper layer of water, but due to its strong water stirring effect, the amount of dissolved oxygen escape is not high (according to the determination of about 0.77 kg oxygen/kW·h), of the dissolved oxygen still passes The aerator is delivered to the lower layer.
2. The rational use of aerators
Aerators are widely used nationwide, but many units are unreasonable when using aerators, or adopt the method of no floating head and no start, convert the aerator to a fish-saving machine, so that the aerator The following methods should be adopted for the conversion of fish-saving machines into aerators:
① The main reason for the hypoxia caused by different weather must be used according to the principle of the aerator. The lack of oxygen in the morning of the next day is mainly due to the large vertical change of dissolved oxygen in the upper and lower water layers during the day. The lower temperature of the lower layer is large during the daytime and the upper water temperature is less dense. The upper and lower water layers cannot be convected immediately, and the supersaturated oxygen in the upper layer is not available. There are many oxygen consumption factors in the lower layer wasted away from the water surface, the surface water temperature at night is reduced, and the density is increased. The upper and lower water layers are properly turned on at noon on a sunny day. Properly connecting the power supply during the sunny day is to use the combined method of biological oxygen and mechanical oxygen delivery, use the upper supersaturated oxygen, and use the water stirring effect of the aerator to transport the large amount of supersaturated oxygen produced in the upper layer phytoplankton photosynthesis to Lower layer, immediately supplement the lower layer of hydrogen and oxygen to reduce the oxygen consumption of the lower layer of water. Although the amount of dissolved oxygen in the upper layer water is lower than before the start-up, the dissolved oxygen in the upper layer can still be saturated by algae photosynthesis in the afternoon. After the natural convection of the pool water at night, the dissolved oxygen in the upper and lower water layers can still maintain a high level, which can alleviate or eliminate the threat of fish floating heads to a certain extent. Proper start-up at noon on a sunny day can not only prevent or reduce the floating head of fish, but also promote the decomposition of organic matter and the propagation of plankton, and accelerate the material circulation of the pond. Therefore, in the main growing season of fish, try to turn on the aerator at noon and make full use of the supersaturated oxygen in the upper water to seize the initiative to improve the water quality. B. Cloudy days and rainy days must be turned on. The lack of oxygen in cloudy days and rainy days is due to the weak photosynthesis of phytoplankton, less oxygen production and high oxygen consumption, so that the dissolved oxygen is in short supply and the fish floats. At this time, it is necessary to give full play to the role of the aerator, use the technology of predicting the floating head, and aerate early. Must be turned on before the fish floating head, directly improve the low peak value of dissolved oxygen, prevent and rescue the fish floating head. C. Can't boot on sunny evening. Turning on the sunny evening will make the upper and lower water layers convect in advance, but increase the oxygen-consuming water layer and oxygen consumption. Its effect is similar to that of thunderstorm in the evening, and it is easy to cause floating head. D. Startup at noon on a rainy day is to turn on the "floating head machine" at noon and on a rainy day. Not only can it not increase the dissolved oxygen in the lower layer of water, but it can also reduce the oxygen production of the upper phytoplankton and increase the oxygen-consuming water layer of the pond. The rate of oxygen consumption in the lower layer of water can easily cause floating heads.
②The technology of predicting floating head must be used in accordance with the specific situation of fish farming at that time, and the aerator should be used reasonably. The start-up time and length of operation of the aerator are not fixed, but it is related to factors such as climate, water temperature, pond conditions, the amount of bait fertilization, and the power of the aerator. According to the specific situation of fish farming at that time, according to the change law of dissolved oxygen in the pond, it should be flexibly grasped and the aerator should be used reasonably.
The boot time can be taken: open at noon on a sunny day, open at early morning on a cloudy day, open at midnight in the middle of the rain, not open in the evening, open early in the morning, and the principle of daily opening in the main growing season of fish.
The running time can be taken as follows: long boot time in the middle of the night, short boot time at noon; hot weather, large area or large load water surface, long boot time, cool weather, small area or small load water surface and short boot time.
3. Reasonable use of aerators according to the season and abnormal conditions
It depends on the season, weather, water quality, water temperature, species, fish activity and feeding situation, stocking density, fertilization and bait. If it rains heavily, the aerator should be turned on in the middle of the night to aerate in time to prevent floating heads. On rainy days, the photosynthesis of phytoplankton is weak, and the floating head is very easy to be anoxic. The aerator should be turned on in the middle of the night and the startup time is long. In summer and autumn, this is the peak season for fish growth. During the day, the water temperature is high, the fish activity is large, the oxygen consumption is large, and it is easy to cause hypoxia. At dawn, you can properly turn on the aerator to increase the amount of dissolved oxygen. If the weather is hot, the boot time is properly extended. When the stocking density is large and the fish grow fast, it is appropriate to extend the start-up time. In order to improve the conditions of the dissolved oxygen pool water, the method of combining noon start and morning start should be used to increase the amount of dissolved oxygen in the water to prevent floating heads. When patrolling the pond, it was found that the fish had abnormal activities, reduced food intake, and signs of floating heads. The aerator should be turned on in time until the fish returned to normal. In case of large temperature difference, it should be turned on in time. In the aquaculture process, the start-up and running time should be flexibly controlled according to specific conditions and water-dissolved oxygen laws (day and night, vertical, horizontal, seasonal changes) to achieve reasonable application, save costs, and increase production efficiency.