The working principle and types of aerators

The main performance indicators of the aerator are defined as aerobic capacity and power efficiency. Oxygenation capacity refers to the amount of oxygen added to the water body by an aerator per hour, in kilograms/hour; power efficiency refers to the oxygenation amount of water that an aerator consumes 1 kWh of electricity, in kilograms/kWh . For example, a 1.5 kW waterwheel aerator has a power efficiency of 1.7 kg/kWh, which means that the machine consumes 1 kWh of electricity and can add 1.7 kg of oxygen to the water body.
Although aerators are more and more widely used in aquaculture production, some fishery practitioners still do not understand its working principle, type and function, and they are blind and random in actual operation. Here it is necessary to understand its working principle first, so that it will be mastered in practice. As we all know, the purpose of using an aerator is to add dissolved oxygen to the water, which involves the solubility and dissolution rate of oxygen. Solubility includes three factors: water temperature, water salt content, and oxygen partial pressure; dissolution rate includes three factors: the degree of unsaturation of dissolved oxygen, the contact area and method of water-gas, and the movement of water. Among them, the water temperature and the salinity content of the water are a stable condition of the water body, which cannot be changed in general. Therefore, in order to achieve oxygen addition to the water body, three factors must be directly or indirectly changed: the partial pressure of oxygen, the contact area and method of water and gas, and the movement of water. In response to this situation, the measures taken when designing the aerator are:
1) Use mechanical parts to stir the water body to promote convective exchange and interface renewal;
2) Disperse water into fine mist droplets and spray them into the gas phase to increase the contact area of ​​water and gas;
3) Inhale through negative pressure to disperse the gas into micro-bubbles and press into the water.
Various types of aerators are designed and manufactured according to these principles, and they either take one measure to promote the dissolution of oxygen, or take two or more measures.
Impeller aerator
It has comprehensive functions such as aeration, water stirring, and gas explosion. It is the most used aerator at present, with an annual output value of about 150,000 units. Its oxygenation capacity and power efficiency are better than other models, but the operating noise is relatively large. It is used for aquaculture in large-area ponds with a water depth of more than 1 meter.

Waterwheel aerator: It has a good effect of increasing oxygenation and promoting water flow, and is suitable for ponds with deep silt and an area of ​​1000-2540 m2 [6].
Jet aerator: Its aeration power efficiency exceeds that of waterwheel type, inflatable type, water spray type and other forms of aerators, and its structure is simple, which can form water flow and stir water body. The jet oxygenation function can make the water body oxygenate smoothly without damaging the fish body, which is suitable for the use of oxygenation in fry ponds
Water spray aerator:It has a good oxygen-enhancing function, can rapidly increase the dissolved oxygen in the surface water in a short time, and also has artistic ornamental effect, which is suitable for fish ponds in gardens or tourist areas.
Inflatable aerator: The deeper the water, the better the effect, and it is suitable for use in deep water.
Inhalation aerator: The air is sent into the water through negative pressure suction, and it forms a vortex with the water to push the water forward, so the mixing force is strong. Its oxygen-enhancing ability to the lower water is stronger than that of the impeller aerator, and its oxygen-enhancing ability to the upper water is slightly inferior to that of the impeller aerator [4].
Eddy flow aerator: Mainly used for oxygenation of subglacial water in northern China, with high oxygenation efficiency [4].
Oxygen pump: Because of its light weight, easy operation and single oxygen-enhancing function, it is generally suitable for fry cultivation ponds or greenhouse cultivation ponds with a water depth of less than 0.7 meters and an area of ​​less than 0.6 mu.