A NOVEL MODEL FOR NITRIFYING TRICKLING FILTERS

A novel mathematical model for nitrifying trickling filters has been d eveloped. The model is based on material balances on the biofilm and t he bulk liquid. The model predicts the profiles of nutrients as a func tion of the operating parameters (volumetric flow rate and feed ammoni a concentration). Based on the assumption that the biofilm consists of an active and an inactive part, and that biofilm detachment occurs wh en the viable bacteria in the inactive biofilm drop below a critical f raction, the model also predicts the biofilm thickness as a function o f filter depth. In order to verify the validity of the model, experime nts using a pilot-scale nitrifying trickling filter were performed. In all cases the comparison between the model predictions and the experi mental data is satisfactory. In particular, the model was found to pre dict the pilot performance for ammonia concentrations encountered in p otable water quite well. The model is ideal for the design of nitrifyi ng trickling filters due to the simplicity of its recursive equations.