Study On The Start-up Of Filter Media And Water Treatment In A Closed Recirculating Aquaculture System

A key to successful recirculating aquaculture system is the use of cost-effective water treatment system components. The biofiltration that has low energy cost and produces little excess sludge is widely applied in the water treatment of recirculating aquaculture system. Since the heart of any biofilter is the filter media, the type of filetr media used strongly influences both the capital and operating costs of the biofilte.In the present study, first research the four biofilter that prime the soft filter media, the flexibility filter media, the half flexibility filter media and the suspend boll filter media establish their function with three different way(nature, sludge and bacterium). The result shows that it takes 45 days to establish the biofilter's function by use the nature way. The NH4-N in the culture wastewater will drop to 0.035mg/L when the system was run 45 days. And there are strong Nitrite-N accumulation in the biofilter if use the nature way to build the biofilter function. And the Nitrite-N peak value can attain 2.8mg/L. Used the bacterium way to build the biofilter's function, in the first 20 days the concentration of the NH4-N drop very fast, and the concentration will drop to 0.86mg/L. But when the system was run 20 days later, the concentration of the NH4-N will keep 0.86mg/L long time. And when used the activated sludge way to establish the biofilter's function, it only takes 30 days the concentration of the NH4-N will drop to about 0.035mg/L and the Nitrite-N accumulation will be not as strong as the nature way. And this research shows that using the activated sludge way to build the biofilter's function is better than the tow other ways.This research also shows that using pack with the suspend boll filter media biofliter use the activated sludge way can easy to build its function and can get more stability biofilm. Using the activated sludge way to building the biofilter which fill with the suspend boll filter media when the system was run to the twenty-seven day the concentration of the NH4-N can drop to 0.033mg/L. And the Nitrite-N accumulation was not very strong. And the other three filter media will expend about 35 days to build their function. This result shows that the suspend boll filter media is better than the other three filter medias. Biofilter packed with suspend boll filter media was used for treatment of aquaculture water for reuse application ,and the establishment of its function and the hydraulic retention time(HRT) how to affect its treatment effect were investigated. The experimentation setup three HRTs. The result shows that use activate sludge cultivated the biofilter filled in simulation culture wastewater, it only takes about one month to establish the biofilter function and that condition of HRT 0.6h as well as the influent NH4-N being 1.98 mg/L is the best of the three HRTs. the biofilter system circulated six days can make the influent NH4-N come down to 0.03mg/L.The Nitrite-N have a short time accumulation but also can be drop to 0.05 mg/L at last. HRT affect the removal of NH4-N, and then affect the removal of Nitrite-N. The removal of CODmn is a little affected by HRT, and the removal rate of CODmn is about 28% in this system.