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Copyright of Pearl River is the property of Pearl River Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Pearl River is the property of Pearl River Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Pearl River is the property of Pearl River Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

With the improvement of aquaculture scale, the disadvantages of traditional aquaculture mode are constantly emerging, including waste and pollution of water sources. On this basis, the recirculating aquaculture system with aeration plug-flow device in pond is an exploration of efficient and energy-saving aquaculture mode, which has been developed rapidly at home and abroad. Water environment, as the place where fish live, is crucial to the growth of fish. A large number of studies have shown that dissolved oxygen, ammonia nitrogen and nitrite are the three important factors that affect the growth of fish. There are synergistic effects among dissolved oxygen, ammonia nitrogen and nitrite. Insufficient dissolved oxygen and high mass concentrations of non-ionic ammonia and nitrite can cause metabolic dysfunction of fish body and decrease of immunity, leading to the occurrence of fish diseases. Therefore, in order to explore the response of fish growth to water environment, and predict the growth rate of fish under the synergistic effect of water environment factors, the experiment was conducted on indoor recirculating aquaculture tilapia test with aerated plug-flow device with a continuous duration of 8 weeks. By changing the aeration flow, three conditions were set up in the experiment to observe the growth of tilapia during the breeding period, and the mass of the fish and water quality parameters such as dissolved oxygen, non-ionic ammonia and nitrite were regularly measured. The results showed that within a certain range, with the increase of dissolved oxygen mass concentration, the food conversion efficiency and specific growth rate of fish increased; with the increase of non-ionic ammonia mass concentration, the food conversion efficiency and specific growth rate of fish decreased. However, due to the small change in nitrite mass concentration and the safe mass concentration range, there was no significant effect on the food conversion efficiency and specific growth rate of fish in this experiment. Based on the results of the experiment, the specific growth rate of tilapia was nonlinearly fitted, and the growth prediction equation of fish was established, with R2 of 0.82. The validity and universality of the equation were verified by the measured data. The growth prediction equation showed that the increase of the initial mass of fish, stocking density, non-ionic ammonia and nitrite concentration could slow down the growth rate of the fish; while increasing the dissolved oxygen concentration could increase the growth rate of the fish. In the current situation of increasingly tight land, intensive farming is often adopted to improve the level of farming. With the increase of aquaculture density, the concentration of non-ionic ammonia and nitrite in the water environment increases, which have a negative impact on the growth rate of fish. It could improve the water environment and promote the healthy growth of fish by increasing dissolved oxygen. Although this prediction model is obtained under the aeration push flow cycle cultivation mode, it is also applicable to the other aquaculture water modes, making the response of fish growth to measurable water environmental factors, which provides convenience and reference for promoting the healthy development of aquaculture fish, the optimization of aquaculture system and the improvement of aquaculture benefits. [ABSTRACT FROM AUTHOR]

In lakes, reservoirs, rivers, estuaries, aquaculture ponds and sewage treatment plants where the dissolved oxygen concentration needs to be increased, aerator is the most important oxygen equipment to maintain the dynamic balance of dissolved oxygen. Among different kinds of aeration facilities, the microporous aeration aerator has been more widely used, because of its large ventilation capacity, strong oxygenation capacity, energy saving and environmental protection, easy installation and strong adaptability. There are many factors that affect the aeration performance of microporous aeration aerator, mainly including external factors and self factors. The microporous aeration aerator uses a microporous aeration tube as its diffuser, but the current study of the effect of the type of the diffuser on the aeration performance of the microporous aeration aerator is almost blank. And conventionally, the microporous diffuser always uses disc-type, but this way is empirically and even blindly adopted. Therefore, in order to explore the effect of the microporous diffuser with different shapes on the oxygenation performance, a series of oxygenation experiments were carried out under different types of air diffuser rolled up by a same length (1.1 m) of aeration tube in laboratory. The type of the microporous diffuser was the main influence factor. The types were linear-type, C-type, S-type and disc-type. The experimental apparatus mainly included glass tank, microporous aeration system, dissolved oxygen meter and computer. The size of the glass tank was 2 m × 0.8 m × 0.8 m (length × width × height). The test was based on the standard test method for oxygen from American Society of Civil Engineers (ASCE) in different water depth and air flow. The air flow rate was set as 0.6, 0.9, 1.2, 1.5, and 1.8 m3/h and the water depth was set as 0.4, 0.55, and 0.7 m. The results show that, under the same water depth and air flow rate, the oxygen volumetric mass transfer coefficient, standard oxygen transfer rate, standard aeration efficiency and standard oxygen transfer efficiency of the linear-type microporous aeration diffuser are the highest. In the 0.7 m water depth, the ranges of the 4 technical indices are 0.853-1.762 h-1, 8.701-17.432 g/h, 6.869-4.146 kg/(kW·h), and 4.912%-3.257%, respectively, while the S-type is the lowest, and the range values are 0.798-1.504 h-1, 6.850-12.627 g/h, 4.444-2.630 kg/(kW·h), and 3.823%-2.339%, respectively. Between the linear-type and S-type microporous aeration diffuser are the C-type and disc-type. The same law is also obtained at another depth of water. It meant that the oxygenation performance of linear-type was the best, while the lowest one was the S-type microporous aeration diffuser. It could be known that it is not the best for the oxygenation effect of the disc-type microporous diffuser, which we have chosen empirically. After the film was covered on the top of tank to cut off the air-free water surface oxygen mass transfer, the values of oxygen volumetric mass transfer coefficients of these 4 types of diffusers were decreased and the degree of descent was different, and the largest decline rates were 12.29%, 8.73%, 12.26% and 6.75%, respectively. So, the influence degree of air-free water surface oxygen transfer on different diffuser types is different. But the best oxygenation effect occurred still under linear-type microporous aeration diffuser, followed by the C-type and disc-type, and the S-type is still the lowest one. And the values of oxygen volumetric mass transfer coefficients in 0.7 m water depth of linear-type microporous aeration diffuser, C-type and disc-type and S-type are 1.693, 1.470, 1.438 and 1.227 h-1, respectively. Therefore, oxygen performance of linear-type microporous aeration diffuser is the best. Based on these conclusions, for the shallow water to oxygenate, the linear-type microporous aeration diffuser is the first to use as aeration equipment, which provides a certain reference value for us in the practical selection of microporous diffuser shape. [ABSTRACT FROM AUTHOR]