Aquaculture plants as Recirculating Aquaculture Systems (RAS), recirculating systems

Aquaculture plants as recirculating aquaculture systems (RAS), recirculation systems. Colasit aquaculture plants for fish, algae or crustaceans are recirculation systems or recirculation systems in tanks. The water is cleaned using integrated water treatment system and returned to the fish tank. 

Recirculation systems consist of holding tanks and subsequent mechanical and biological water treatment, e.g., using drum filters and moving bed filters. Disinfection with UV irradiation or ozonation is offered as an option. Water treatment in recirculation systems is necessary to remove accumulating feed residues, faeces and metabolic end products - primarily "waste" products from protein metabolism - from the system. Otherwise, harmful concentrations of pollutants arise for the animals in the tanks.

The Recirculating Aquaculture System (RAS) is characterised by:

• Controlled system
• Low water consumption
• Location-independent
• Year-round production 
• Shortened production cycle
• Low wastewater quantities
• Natural waters are not contaminated

Despite high operating and investment cost, RAS systems are considered sustainable because wastewater from RAS systems can be discharged via the sewer system and does not contribute any nutrients to natural water bodies. 

In comparison, flow-through systems offer advantages thanks to their simplicity and the lower investment capital requirement. However, they generate high energy costs, use a great deal of water and emit large quantities of water contaminated with nutrients into the environment.