Tag RAS

The water quality in recirculating aquaculture systems is generally a function of the tank size, biomass, feed inputs and waste treatment efficiency. Adequate biofiltration can control the build-up of ammonia-nitrogen and nitrate-nitrogen in the systems. 

Dozens of land-based, closed-containment salmonid RAS systems are coming on line. New projects are bringing new principles into the salmon industry. Industry expansion hinges upon the development of pollution-mitigating technologies to reduce nutrients in effluents. 

The benefits realized by recirculating aquaculture systems – including enhanced fish growth, product quality and survival, as well as reduced treatment costs – have made the RAS approach an important production trend. 

Geotextile bags used in combination with polymer flocculant aid chemicals can provide effective primary treatment of recirculating aquaculture system effluent. Much of the suspended solids that carry the majority of the organic load within the effluent can be captured by these systems. 

A study to evaluated operating practices and system designs that could potentially enhance depuration of off-flavors from Atlantic salmon cultured in a semi-commercial-scale freshwater recirculating aquaculture system. 

The ability to maintain adequate oxygen levels can be a limiting factor in carrying capacities for RAS. The amount of oxygen required is largely dictated by the feed rate and length of time waste solids remain within the systems. 

A unique pilot project supported by northern Chile’s biggest power-generating company and the Undersecretary of Fisheries and Aquaculture is raising cobia in a recirculating aquaculture system in the desert. 

Today’s aquaculture industry is rapidly adopting recirculating aquaculture systems (RAS) for hatchery and nursery applications. Recently, there has been a move to combine RAS technology with the floating raft aquaponics. 

The presence of compounds such as geosmin and 2-methylisoborneol (MIB) in recirculating aquaculture systems (RAS) can result in earthy or musty off-flavors in salmonids raised in the systems. 

Studies on improving water quality in recirculating aquaculture systems has identified ozone as an excellent solution for an optimal water environment. 

One promising new technology for dewatering aquaculture solid waste is the use of geotextile bags: porous, sealed tubular containers constructed of high-strength, woven polyethylene material. 

Floating closed-containment systems incorporate low-pressure pumping, oxygen supplementation, solid-waste separation and efficient feed management. 

Healthy populations of both ammonia- and nitrite-oxidizing bacteria must be present in aquaculture systems to support the nitrification of potentially toxic ammonia to nitrite, with further oxidation to less problematic nitrate. 

Smolt production in Norwegian hatcheries will likely increase during the next decade to answer salmon grow-out needs. Farmers are converting existing flow-through systems to partially or fully incorporate recirculation technologies. 

Nitrifying bacteria readily form biofilms on surfaces, and colonization by these important bacteria on the interior walls of RAS production units likely provides an additional source of nitrification.