February 15-18, 2009 Washington State Convention Center Seattle ...

EFFECTS OF TEMPERATURE REGIME ON NITROGEN DEGRADATION: LABORATORY
AND MODELING RESULTS
Milton Saidu*, Steven G. Hall, Ron Malone and Terrence Tiersch
Biological and Agricultural Engineering
LSU AgCenter
Baton Rouge, LA, 70803 USA
msaidu1@lsu.edu
Temperature is a factor in growth of aquatic species. Previous work had considered how temperature may affect nitrogen
degradation in biofilters and other components of aquaculture systems. This work used a series of laboratory (40 liter) and
pilot scale (250 liter) temperature controlled tank systems (Figure1) to assess effects of different steady state and variable temperature
regimes on nitrogen degradation. A series of protocols were used to assure controlled conditions, including unique
heat exchangers, computer controlled heating and cooling and cleaning and measurement protocols which provided enhanced
replicability of experiments.
Steady state temperatures of 13, 20 and 30 each showed significant differences (Figure 2) in ammonia degradation rates. Diurnal
sinusoidal 20±3 and 30±3 temperature regimes also revealed significant differences and suggest that this level of variation
may enhance, not limit degradation. Step input studies provided similar evidence, while mixing beads acclimated at different
temperatures from 13 to 30C appeared to enhance degradation. Modeling studies helped clarify these results and provided
predictive tools for future design and management of biofiltration systems in controlled or natural settings.
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