Influence of medium composition on the characteristics of a denitrifying biofilm formed by alcaligenes denitrificans in a fluidised bed reactor

摘要

The influence of the ratio carbon/nitrogen and phosphorus concentration on the performance of a biofilm fluidised bed reactorused for denitrification and on the properties of the biofilm was studied. Although the removal efficiencies of C and N reachedsteady-state values, the thickness of the biofilm steadily increased. The dry density of the biofilm did not seem to be dependenton the loading conditions, although a denser biofilm was obtained when there was no nutrient limitation that corresponded to thecomplete removal of nitrate and carbon. The composition of the biofilm in terms of proteins and polysaccharides changed withthe C/N ratio and P concentrations. Higher denitrifying activities, which were obtained with increasing P concentrations, wererelated with higher protein content, since metabolism was shifted from polysaccharide production towards cell production. Thethickness and the density of the biofilms were related mainly with the shear stress in the reactor and the composition of biofilmswas dependent on the composition of the medium and related with higher activities of the microorganisms.