INTERPRETATION OF BACTERIAL ACTIVITIES IN NITRIFICATION FILTERS BY A BIOFILM MODEL CONSIDERING THE KINETICS OF SOLUBLE MICROBIAL PRODUCTS

Activities of heterotrophic bacteria in nonsteady-state biofilms were evaluated using a simplified biofilm model in which formation and exch ange of soluble microbial products (SMP) by nitrifiers and heterotroph s were considered. The model was applied to experimental results for a trace-level substrate removal. The model predictions indicated that S MP from nitrifiers contributed to supporting heterotrophic growth and their substrate removal potential. The biological interactions were mo re significant in cases of low influent substrate COD concentrations a nd increased with higher influent ammonium concentration. The introduc tion of SMP kinetics into the model captured the key aspects of remova l and formation of COD components in biofilms receiving low influent s ubstrate concentrations, such as nitrification filters for drinking wa ter treatment and wastewater reuse.