Reserch On Recirculating Aquaculture Bio-oxidation System Construction And Effect

With the devolopment of the modern fishery, enclosed recirculating aquaculturesystem was focused on small occupation of land, water saving, free of environmentalimpact,no pollution. The key to successful recirculating aquaculture system was theuse of water treatment system.while the biological filter was the kernel technique ofwater treatment system. In this study,with the purpose to build scientific recirculatingaquaculture system, we studied the water treatment efficiency of different kinds ofbiological filter media, main environmental factors,biological filters and differentscreens of drum microfilter respectively.The results were as follow:(1) A comparison study of the purification effect of Zeolite,fibre-ball,plastic ringpacked into different biofilters was performed. The results showed the maturationtime of biofilm for the filler-ball as biological filter media was24days,faster thanthat of Zeolite and plastic ring.whose maximum fish load was405kg/m3, which was118.4%and128.6%of that of zeolite and plastic ring respectively；the removal ratesof NH4+-N、 NO2—-N、 COD were0.191mg.L-1.h-1、0.189mg.L-1.h-1and4.19mg.L-1.h-1by fibre-ball,which were significantly higher than those of others。Theresearch showed that compared with the Zeolite and plastic ring. fibre-ball was a kindof substrate with high specific surface area and similar density with water, highpurification efficiency、 low cost、 easy attaching、 high fish loads、 easywashing,which had a more effective way in practical production.(2) Using the fibre-ball as biological filter media, we studied the purification effect ofthe biological filler at different dissolved oxygen (8mg/L,12mg/L,16mg/L) underthe same conditions.Five glucose levels of0%(the blank),30%,40%,50%,60%weredesigned to study the effect of different carbon-nitrogen ratio on the water purificationand the maximum fish load of biological filter media.The results showed that thecuring time of dissolved oxygen at12mg/L was the shortest, which was18days,while DO. at16mg/L was20days, DO. at8mg/L was24days.The removalrates of NH4+-N、NO2—-N of the group of DO. at12mg/L and16mg/L (P＞0.05) wassignificantly greater than that of group at8mg/L (P <0.05).The removal rates ofCOD of the group of DO. at8mg/L and12mg/L was significantly greater than groupat16mg/L (P <0.05).In glucose levels of the40%group the biggest fish load couldreach537kg/m-3and was132.5%of that of the blank group.The results showed thatdifferent dissolved oxygen had an obvious effect on the purification of biologicalfiller in an enclosed recirculating aquaculture system, The curing time of the group (DO. at12mg/L) is the fastest,and could maintain low ammonia nitrogen, nitrite,COD level to satisfy the cultured species;Adding glucose can enhance the maximumfish load, the most optimal adding was40%of the amount of diets.(3) Submerged biofilter as control, purification effect of drawer biofilter and floatingbiofilter in recirculating aquaculture system.The result showed that at the sametemperature、pH and dissolved oxygen conditions,the curing time of drawer biofilterand floating drawer were19days、18days respectively, faster than that of immersiondrawer(22days);the removal rates of NH4+-N、NO2—-N、COD of drawer biofilterwere0.599mg.L-1.h-1、0.561mg.L-1.h-1、13.00mg.L-1.h-1,while floating filter were0.491mg.L-1.h-1、0.351mg.L-1.h-1、9.885mg.L-1.h-1, both were significantly greaterthan that of the immersion biofilter(P<0.05); the maximum fish load was the drawerbiofilter, which could reach443kg/m-3and was109.3%and105.4%of that of thefloating biofilter and immersion biofilter respectively.The study showed that in therecirculating aquaculture system,the treatment of drawer biofilter and the floatingbiofilter were better than immersion,while the drawer biofilter was best and worthy ofapplication and promotion.(4) In this experiment we choose different screen of micro-screen drum filter(120﹟、260﹟、420﹟) in recirculating aquaculture system to study the relationship betweenthe screen and the removal ratio of TSS and influence on the efficiency of watertreatment.The result showed that the removal ratio of total suspended particlesof the120﹟、260﹟、420﹟were38.8%、47.3%、67.8%respectively and the maximum fish loadswere132.1%、143.1%、161.5%of that of before installation..