ELIMINATION OF NITROGEN IN 2 FLOODED AND STATICALLY PACKED-BED BIOFILTERS WITH AEROBIC AND ANAEROBIC MICROSITES

Nitrogen removal efficiency was studied in a biofilter system consisti ng of two flooded, statically packed bed biofilters (reactors A and B) with aerobic and anaerobic microsites. During the experimental period the reactors were integrated into a quasi-closed recirculated fish cu lture system. In two experiments the degradation efficiency of dissolv ed oxidized nitrogen compounds (NOx-N = N-2(-)-N+NO3--N) was measured with and without oxygen supply. The oxygenation system consisted of si licone membranes integrated into the filter-bed and supplied with tech nical oxygen. The carbon source during the experimental period was met hanol. The efficiency of NOx-N removal for reactor A (without oxygenat ion) was 55%. With oxygenation, degradation efficiency of reactor A in creased to a maximum of 86%. The maximum NOx-N degradation efficiency of both biofilters (reactors A and B) reached 97% when connected in se ries. Shifting of the bacterial populations as well as a linkage of th e nitrogen transformations in the aerated and unaerated microsites are discussed as possible reasons for the higher nitrogen removal rates.