Study On Water Dissolved Oxygen Techniques And Its Application In Living Aquatic Transportation

Bubbleless aeration using hollow fiber membrane contactor is a novel aeration method without visible bubbles. With the flowing of pressure air or pure oxygen in the lumen-side and water in the shell-side in a opposite direction, oxygen can diffuse into the water through the membrane micropores because of the oxygen pressure difference. There is a large amount of pores which size is around 10-1μm in the hydrophobic hollow fiber membrane. In the shell-side, due to the hydrophobicity of the material and capillary effect, water cannot permeate into the lumen-side of the membrane. While in the other side, gas filling in micropores can transfer into water in high efficiency since the relatively large contact area between gas phase and liquid phase, the hollow fiber membrane contactor shows a good performance of gas mass transfer. Compared to the traditional bubble aeration, the bubbleless aeration has obvious advantages, such as high efficiency of oxygen transfer, no bubble, filtering bacteria and low power consumption. Consequently, this novel aeration method can be used to solve the hypoxic water problems during the long distance and high density transportation of living aquatic products.Firstly, the oxygen transfer efficiency of bubbleless aeration using hollow fiber membrane contactor is compared to that of sealed bag aeration and air blast aeration. The results show that bubbleless aeration represents a good oxygenation capacity. It can significantly increase the dissolved oxygen in a short period of time. It fully proves the high efficiency of bubbleless aeration in water oxygenation.Secondly, the hollow fiber membrane module is used as a contactor, and the air supply is pure oxygen. Bubbeless aeration experiment has been done and a novel mass transfer model of the process is established. The result shows that with the pressure increased, the oxygen mass transfer coefficient increases. In other way, the oxygen mass transfer coefficient increases dramatically, and then decreases dramatically, finally increases gradually when the water flow velocity increase. This is differ from traditional rule. Consequently, it's demanded to choose a appropriate liquid flux to achieve the optimum result when hollow fiber membrane bubbeless aeration utilized. It fully proves the scientificity of bubbleless aeration from the theory of mass transfer.Lastly, in this paper, the novel aeration method is firstly applied in the field of living aquatic products transportation. Aimed at tackling survival rate of living aquatic products in long distance transportation affected by dissolved oxygen and currently fashionable living creature gift market, a gift packed transporting apparatus is designed. The experiment of high density transportation of living aquatic products shows that the survival rate is above 95%. Consequently, this apparatus is effective in high density transportation of living aquatic products. It fully proves the practical applications of bubbleless aeration.