The startup process for moving bed bio-reactors (MBBR) in freshwater recirculating aquaculture systems (RAS) within the Norwegian aquaculture industry

Abstract

Recirculating aquaculture system (RAS) technology is becoming increasingly popular in today’s growing aquaculture industry, as it provides further expansion on already limiting good freshwater resources in a controllable and environmentally friendly manner. There are several different biofiltration technologies existing in RAS, of which moving bed-bio reactors (MBBR) are the most prevalent. Research has shown that MBBRs have, amongst other benefits, a small footprint and a low maintenance. The startup process of such systems are, however, rather time consuming and complicated, as they cultivate and grow live nitrifying bacteria, and therefore need further looking into and understanding. Two experiments where performed in this thesis, taking a deeper look at the startup process in detail, with regard to startup time, bacterial growth and toxic product peaks. The experiments included registering and documenting the startup process of a large scale industrial MBBR delivered by Krüger Kaldnes to the Norwegian aquaculture industry and taking a deeper look at different startup additives and conditions through a small scale experiment. Results showed a startup time of 34 days for the large scale experiment to approximately 64 days for the small scale experiment, in addition to ways of improving future startup processes.