Influence of Substrate Concentration on the Growth and Activity of a Nitrifying Biofilm in a Submerged Biofilter

Abstract

Abstract The influence of substrate concentration over the concentration and activity of the nitrifying biofilm in an Up-flow Biological Aerated Filter (UBAF) is presented. Two effects, nutrition and inhibition, were observed on the biofilm activity and both were respectively associated to the cationic and neutral form of the substrate. The nutritional effect of the substrate was expressed and quantified as the specific ammonium concentration as g NH4 +-N kg VAS−1 (Volatile Attached Solids), and the inhibition as the specific free ammonia concentration g NH3-N kg VAS−1. Ammonium concentration ranged between 50 and 150 g NH4 +-N m−3. When surpassing a specific ammonium concentration of 3 g NH4 +-N kg VAS−1 in the system the specific activity of ammonia and nitrite oxidizers decreased although the biomass concentration remained constant. In the other way when surpassing a free ammonia concentration of 0.5 g NH3-N kg VAS−1 the biofilm concentration decreased and ammonia oxidizers showed greater activity than nitrite oxidizers occurring nitrite accumulations in the system up to values of 90 %. Keywords: Inhibitionnitrificationammoniabiofilmbiofilter