Operation of a Retained Biomass Nitrification System for Treating Aquaculture Water for Reuse,
PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF AGRICULTURAL ENGINEERING
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A series of experimental trials were conducted in which a variety of polyurethane materials of differing pore size were evaluated a s a media for nitrifying filters used in treating water in a trout hatchery. These filters were found to be capable of ammonia oxidation rates ranging from 80-180 mg-Ndayliter of liter volumes. These rates represent an order of magnitude increase over removal rates in conventional rock filters operating at influent ammonia levels at or below 0.5 mgliter. These rates were, however, 50 to 100 lower than the rates observed for a similar filter design operating under laboratory conditions. the difference was attributed to increased heterotropic fouling experienced during the field operations. The optimum design for the field unit was found to be an initial stage of open pore media to accept the heterotropic loading followed by a second stage of fine pore material to allow for complete nitrification. Such filters may be operated at detention times less than four minutes achieving well over 90 ammonia removal.