Hadath Tilapia Farm, Lebanon, year 2000


The SAFF–RAS is a highly integrated novel Recirculation Aquaculture System (RAS) designed to achieve high Production : Capacity Ratio’s (P : C ratio) upwards of 6:1 raising table sized Nile tilapia (350g) using as little energy as possible to produce 1kg of market ready tilapia in the range 1.0-1.2 kWh-1 kg-1. See Farmers Weekly article for more details on the prototype (click here…).
The system is entirely low pressure air driven using one (plus coupled standby) low pressure high speed centrifugal blower (HSCB) to drive one or more rotating biological contactors (RBC's), where in recent times SAFF has replaced RBC’s with Moving Bed Biofilters (MBB). Here specially designed airlift pods are used to pull water though a centrally located water reconditioning system and controllable in-tank horizontal water velocities (15-40cm-1 sec-1) are generated by specially fabricated medium bubble airlift aerators.
The major mechanisms for water reconditioning include an efficient compact Lamella Separator (LS) followed by the conversion of Total Ammonia-Nitrogen (TAN) into Nitrates (NO3_N) via a MBB, replacing the 1st generation SAFF-RAS which used Rotating Biological Contactors (RBC’s), and finally the use of a floating foam fractionator as a main stream treatment to reduce Total Organic Carbon (TOC) system loading. Additional side-stream treatments are applied to achieve a higher degree of water reuse.
The use of pure oxygen is unnecessary due to the high oxygen transfer of a tri-functional efficient airlift aerator design (aeration, carbon dioxide stripping and horizontal water movement) and the proper selection and use of a High Speed Centrifugal Blower (HSCB) which achieves combined motor and compressor efficiencies in the range 60-75% capable of holding > 65% saturation during peak oxygen demand achieving a Standard Aeration Efficiency (SAE) > 2.5kg-1 oxygen kWh-1.