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item Pfeiffer, Tim

Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: 5/20/2001
Publication Date: 6/20/2001
Citation: Lenger, T.A., Perschbacher, P.W., Pfeiffer, T.J. Bead filter enhances recirculating aquaculture systems for tilapia production. Global Aquaculture Advocate. 2001.v.4(3).p.40-41.

Interpretive Summary: "Interpretive Summary not required"

Technical Abstract: Recirculating aquaculture systems (RAS) are gaining interest due to their decreased requirements for land and water, and their ability to be located close to markets. Small-scale farmers have begun raising Tilapia indoors for local markets using recirculating technology. One important water treatment process in recirculating aquaculture systems is biofiltration. Biofiltration s the treatment step that involves the conversion of ammonia from uneaten feed and metabolic waste products to nitrate, the non-toxic byproduct of ammonia. The biofiltration performance of a bubble-washed filter using floating plastic media was evaluated in a RAS for growing Tilapia in a greenhouse. The performance of a 0.06 m3 bead filter was evaluated at feeding rates of 450, 675, and 900 g/day. The filter performance was evaluated by calculating the volumetric total ammonia nitrogen (TAN) conversion rate (VTR). At each of the three feeding rates tested, the bead filter was able to maintain TAN concentrations at acceptable levels for Tilapia culture. An increase in VTR was observed six hours after backflushing at each of the three feeding rates due to decreased solids in the bead filter and consequently increased chemical diffusion within the biofilm. VTR dropped after six hours at the feeding rate of 450 g/day and after 12 ho7urs at the 675 and 900 g/day feed rates. The decrease in VTR was mainly a result of solids accumulation in the filter bed and reduction in flow through the filter. The bead filter operated at 66% of design performance criteria. Filter TAN removal ranged from <100 g TAN conversion per m3 per day immediately after filter backflushing to above 225 g TAN removal per m3 per day 6 to 12 hours after feeding and filter backflushing. Filter performance can be improved by increasing filter backflushing and improving prefilter solids capture.