Comparison of Column Aerators and a Vacuum Degasser for Treating Supersaturated Culture Water

Abstract

Supersaturation of nitrogen gas in water is a common problem in fish culture; mild cases cause stress and severe incidences cause gas bubble disease. Numerous techniques have been proposed for the elimination of excess gas. A vacuum degasser, a column aerator, and a combination of the two aeration systems were evaluated for treating supersaturated well water at the La Crosse (Wisconsin) National Fishery Research Laboratory. The degasser, the column aerator, and the combined systems effectively reduced nitrogen gas from about 133% to near 100% of saturation. However, the vacuum degasser also decreased the dissolved oxygen from 27 to 22% of saturation, whereas the column aerators increased the oxygen level to over 91 % of saturation. The column aerator system is recommended because it is easy to construct, reasonable in cost, requires little maintenance, consumes no energy other than head pressure, and is highly efficient for altering concentrations of nitrogen and oxygen to levels suitable for fish culture.