Particle sieve analysis for determining solids removal efficiency of water treatment components in a recirculating aquaculture system

Recirculating aquaculture systems offer potential finfish production units for small-scale entities as well as large-scale operations. However, the water treatment components of such systems require efficient and proper operation to assure successful production. This study evaluated the solids removal ability of three water treatment components in a two-tank recirculating aquaculture system (28 m3) utilized for the warmwater production of tilapia. The components include a swirl separator, a floating plastic bead bioclarifier, and a fluidized sand filter. Sampling was conducted at five different points in the system with each sample volume being serially fractionated through sieves in size ranging from 23 to 500 μm. Total suspended solids analysis was completed on each sample set to determine the particle size distribution of the influent and effluent water and removal efficiency of each component. The removal efficiency of the swirl separator was over 90% for particles larger than 250 μm and the propeller-wash bead filter had removal efficiencies greater than 85% for particles larger than 55 μm. The fluidized sand filter had the best removal for the smaller size particles with over 65% removal efficiency for particles between 23 and 55 μm. The overall reduction in total suspended solids for the treatment loop of the three components of this small-scale experimental unit was over 85% and adequately removed the suspended solids from the recirculating water for tilapia growout production.