Design An Aeration Plug-flow Device And The Effects Of Its Operation On In-pond Raceway System

With the rapid development of China's economy,aquaculture has also brought a series of environment problems while aquaculture production is increasing.For example:(1)The issue of water resources waste is getting worse;(2)A large amount of aquaculture wastewater is discharged without treatments;(3)The residual feed and accumulated excrement are discharged randomly,which leads to serious contamination of water.In view of these,we designed the indoor in-pond raceway system(IPRS)in the laboratory,where the ecological function zones will keep independent,then the fish production will be improved and water quality will be more purified.At the same time,we also designed the aeration plug-flow device,which is the core and power in this system.The main function of the aeration plug-flow device is to increase oxygen concentration in the water and push water to flow forward.However,there are some details to be studied until the aeration plug-flow device was promoted to actual field sites.For example:(1)How is the effect of aeration plug-flow device on flow velocity?And how is the distribution of flow field?(2)How is the ability of impulse force of the aeration plug-flow device?(3)How much can the dissolved oxygen be supplied into water body by aeration plug-flow device?And how is the distribution of dissolved oxygen concentration in aquaculture tank?(4)How is the effect of aeration flow rate on feed coefficient and fish quality?(5)How is the effect of aeration flow rate on water quality in aquaculture system?In view of these problems,we took tilapia as a feeding object and conducted a series of experimental studies in indoor in-pond raceway system.A large number of preliminary experiments were tested before formal tests,we determined to measure the flow field,water quality of water body,the growth indicators and biochemical indicators of tilapia under different aeration flow rate for 56 days,and analyzed the variation between indicators and aeration flow rate and feeding time.The results of this paper were as follows:(1)The distribution of the longitudinal vertical velocities in the raceway with the aeration plug-flow device was different from typical open channel.The vertical velocity stratification was more obvious and both whirlpool's long and short axis were decreased with Q_a increase.But water resistance time was gradually reduced with Qa increase.(2)The growth,rate level and feed coefficient rate of tilapia increased firstly and then decreased with Q_a increase.When aeration flow rate was 30L/min,tilapia had the best growth,rate level and feed coefficient rate.(3)The activity of aspartate transaminase,alanine aminotransferase,alkaline phosphatase,lactate dehydrogenase,total protein and albumin increased was increase with Q_a increase.But the concentration of triglycerides decreases and the total cholesterol concentration increases with the amount of harmful substances increases in the water.Aeration flow rate has little effect on glucose concentration.(4)There was no correlation between dissolved oxygen concentration and aeration flow rate without fish,and was mixed evenly in the direction of horizontal and vertical.However,if we cultured tilapia,the dissolved oxygen concentration decreased with feeding time increased when aeration flow rate was 0L/min.And obviously,a certain of aeration flow rate could fully meet the direct consumption of fish and the nitrification oxygen consumption of ammonia.(5)There is a positive linear correlation between dissolved oxygen and pH,but there is no correlation between dissolved oxygen and water temperature,conductivity,and redox potential.The dissolved oxygen and nitrate decreased with feeding time increased,and the daily reduction value decreased with aeration flow rate increased.This article combined the theories of ecological hydraulics,water environment and aquaculture to study the effects of different aeration flow rate on flow field,water quality and fish physiological indicators in recirculating aquaculture system.So,the results will supply some technical reference for the in-pond raceway system being popularized into the whole country.