Tech Talk 99
Fish and invertebrate wastes are comprised of uneaten feed, fecal material, algae, fish scales, organic debris, etc. The solid wastes are characterized by particle size and density. Aquaculture wastes vary among between species and applications. Even a change in fish food brands, or going from sinking to floating food, can make profound changes in waste characteristics.
Removal of fish wastes is especially important in recirculating systems, as suspended solids can cause disease, damage gills, foul biofilters, increase oxygen demand, raise ammonia concentrations and cause off-flavor. The removal of suspended solids can be done by gravatational settling (sedimentation tanks, tube settlers, etc.) and physical separation (granular filters, screening, cartridge and bag filters), plus affinity bead filtration, vegetable filters and others. The smallest solids may be removed using foam fractionation, diatomaceous earth filtration or membrane filtration.
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