EVALUATION OF THREE BIOLOGICAL FILTERS SUITABLE FOR AQUACULTURAL APPLICATIONS

Abstract

ABSTRACT A staged rotating biological contactor (RBC), packed tower (PT, trickling filter) and fluidized bed reactor (FBR) were tested simultaneously using common water from a fish culture tank. The culture tank was stocked with channel catfish ( Ictalurus punctatus ) at three different densities (approximately 227, 113 and 57 kg/m 3 ) to provide solute concentrations in the filter influent similar to those expected under intensive culture practices. Mean concentrations of total ammonia nitrogen (NH 4 +‐N + NH 3 ‐N) in the culture tank were 1.46 (3.50‐0.42), 1.26 (1.78‐0.95) and 0.36 (0.48‐ 0.28) mg N/liter at the respective stocking densities. The RBC provided the best nitrification efficiencies (74%, 82% and 76%, respectively). The efficiency of the PT (23%, 42% and 51%) was somewhat better than the FBR (8%, 28% and 32%). The rate of ammonia removal across the entire RBC was 0.79, 0.63 and 0.19 g N/m 2 d ‐1 , with removal across the first two stages of 1.31, 1.15 and 0.31 g N/m 2 d ‐1 . The PT provided arranonia removal of only 0.25, 0.32 and 0.14 g N/m 2 d ‐1 . Dissolved oxygen, nitrite, nitrate, pH, alkalinity and chemical oxygen demand analysis was also performed.