Effect of biocarrier material on nitrification performance during start-up in freshwater RAS

Biofilters are key components in recirculating aquaculture systems (RAS). For ensuring cost-efficient function of biofilters, characteristics biocarriers such as shape, material, surface area, density, longevity, and price needs to be evaluated. In this study, we compared otherwise identical made polyethylene (PE) against ones polypropylene (PP) PP with three different levels pigment (carbon black) addition (without added pigment, semi-pigmented, fully-pigmented). The four types were tested 12 parallel moving bed bioreactors under conditions receiving water from a semi-commercial freshwater RAS rainbow trout. Measurements total ammonium nitrogen (TAN) nitrite-nitrogen (NO 2 - -N) removal rates nitrification kinetics carried out by spiking events NH 4 Cl or NaNO two, four, six weeks after start-up. results showed all biofilters removed TAN only two operation, that had shorter maturation time, reaching their maximum rate at week 4, while PE reached equal 6. generally lower NO -N first-order reaction constants than biofilters. Pigmentation level minor effect on kinetics, fully pigmented initially found have first order for semi-pigmented without pigment. Overall, the suggest is inferior biocarrier material PP, due longer start-up period nitrite accumulation, which might related differences between these materials. Furthermore, indicate does not provide any extra benefit nitrification. • Polypropylene reach faster ones. Polyethylene can lead accumulation during biofilter biocarriers.