The purpose of this study is to reduce the toxicity of aquaculture farm through nitrification and treating nitrogen to achieve stable water quality by using recirculating aquaculture system(RAS). First, the effect of nitrogen sources and heavy metals on zebrafish(Danio rerio) has been investigated b...
The purpose of this study is to reduce the toxicity of aquaculture farm through nitrification and treating nitrogen to achieve stable water quality by using recirculating aquaculture system(RAS). First, the effect of nitrogen sources and heavy metals on zebrafish(Danio rerio) has been investigated by performing the acute toxicity test. Second, a lab scale RAS was conducted to compare the change of nitrogen concentration in breeding water by zeolite, volcanic stone and expanded polypropylene(EPP) media. Finally, opened system with inflow and outflow was conducted to compare with the RAS. As a result of acute toxicity test, 96hr-LC50 of ammonia, nitrite were 168 and 138.21mg/L. And 96hr-LC50 of nitrate was not detected. 96hr-LC50 of free ammonia(FA) and free nitrous acid(FNA) were 2 and 0.20mg/L, respectively. They showed higher toxicity than ammonia and nitrite since the fraction of FA and FNA are seriously affected by pH and nitrogen concentrations. Besides, 96hr-LC50 of Hg was 5.86μg/L and Cu, Cd, Zn were 0.12, 7.40 and 11.90mg/L, respectively. The ammonia concentration was maintained below 0.5mg/L after 100hr by using RAS with all kind of media. In the case of EPP media, the concentration of nitrite was initially increased and decreased after 100hr. In addition, there was no difference in ammonia removal rate among three kinds of media. In the opened system, the ammonia removal efficiency of zeolite and volcanic stone media were 87.65, 94.92%, whereas EPP media was 24.20%. Nitrite concentration was decreased after 200hr using zeolite media. Ammonia concentration was decreased after 300hr, and nitrite concentration began to increase at the same time when using EPP media. RAS achieved stable nitrification state four times faster than the opened system. Using RAS can reduce ammonia toxicity and minimize emissions of pollutants in aquaculture.
The purpose of this study is to reduce the toxicity of aquaculture farm through nitrification and treating nitrogen to achieve stable water quality by using recirculating aquaculture system(RAS). First, the effect of nitrogen sources and heavy metals on zebrafish(Danio rerio) has been investigated by performing the acute toxicity test. Second, a lab scale RAS was conducted to compare the change of nitrogen concentration in breeding water by zeolite, volcanic stone and expanded polypropylene(EPP) media. Finally, opened system with inflow and outflow was conducted to compare with the RAS. As a result of acute toxicity test, 96hr-LC50 of ammonia, nitrite were 168 and 138.21mg/L. And 96hr-LC50 of nitrate was not detected. 96hr-LC50 of free ammonia(FA) and free nitrous acid(FNA) were 2 and 0.20mg/L, respectively. They showed higher toxicity than ammonia and nitrite since the fraction of FA and FNA are seriously affected by pH and nitrogen concentrations. Besides, 96hr-LC50 of Hg was 5.86μg/L and Cu, Cd, Zn were 0.12, 7.40 and 11.90mg/L, respectively. The ammonia concentration was maintained below 0.5mg/L after 100hr by using RAS with all kind of media. In the case of EPP media, the concentration of nitrite was initially increased and decreased after 100hr. In addition, there was no difference in ammonia removal rate among three kinds of media. In the opened system, the ammonia removal efficiency of zeolite and volcanic stone media were 87.65, 94.92%, whereas EPP media was 24.20%. Nitrite concentration was decreased after 200hr using zeolite media. Ammonia concentration was decreased after 300hr, and nitrite concentration began to increase at the same time when using EPP media. RAS achieved stable nitrification state four times faster than the opened system. Using RAS can reduce ammonia toxicity and minimize emissions of pollutants in aquaculture.
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