Combined denitrification and phosphorus removal in a biofilter

A lab-scale biofilter was run continuously for 11/2 years for combined deni trification and phosphorus removal. Alternation between anaerobic and anoxi c (nitrate) conditions was used to obtain an enriched culture of denitrifyi ng, phosphate accumulating organisms. Batch experiments were performed to t est the importance of diffusion and zonation in the biofilm. Half- and zero -order anaerobic phosphate release and anoxic phosphate uptake rates were v erified, which was taken as an indication of a zonated biofilm. To investigate the practical applicability of the process, the development of a computer model is necessary due to the high complexity of the process. AQUASIM is suitable for this purpose. The model can provide insight into w hat goes on inside the biofilm and act as a tool when predicting required t ank sizes, optimal phase lengths and biofilm thickness etc, for a large-sca le system. For control of the process, on-line measurements and computer co ntrol of the system are essential.