Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6381329 | Aquacultural Engineering | 2015 | 9 Pages |
Abstract
It was found that a low nominal alkalinity (10Â mg/L as CaCO3) led to a significantly higher steady-state TAN concentration, compared to when 70 or 200Â mg/L alkalinity was used. The mean areal nitrification rate was higher at the lowest alkalinity; however, the mean TAN removal efficiency across the MBBR was not significantly affected by alkalinity treatment. The CO2 stripping efficiency showed only a tendency towards higher efficiency at the lowest alkalinity. In contrast, the relative fraction of total inorganic carbon that was removed from the RAS during CO2 stripping was much higher at a low alkalinity (10Â mg/L) compared to the higher alkalinities (70 and 200Â mg/L as CaCO3). Despite this, when calculating the total loss of inorganic carbon from RAS, it was found that the daily loss was about equal at 10, and 70Â mg/L, whereas it was highest at 200Â mg/L alkalinity. pH recordings demonstrated that the 10Â mg/L alkalinity treatment resulted in the lowest system pH, the largest increase in [H+] across the fish culture tanks, as well as giving little response time in case of alkalinity dosing malfunction. Rapid pH changes under the relatively acidic conditions at 10Â mg/L alkalinity may ultimately create fish health issues due to e.g. CO2 or if aluminium or other metals are present. In conclusion, Atlantic salmon smolt producers using soft water make-up sources should aim for 70Â mg/L alkalinity considering the relatively low loss of inorganic carbon compared to 200Â mg/L alkalinity, and the increased pH stability as well as reduced TAN concentration, compared to lower alkalinity concentrations.
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Related Topics
Life Sciences
Agricultural and Biological Sciences
Aquatic Science
Authors
Steven T. Summerfelt, Anne Zühlke, Jelena Kolarevic, Britt Kristin MegÃ¥rd Reiten, Roger Selset, Xavier Gutierrez, Bendik Fyhn Terjesen,