Effect of Biofilm Architecture

Biofilm-based phosphorus recovery can improve the robustness of conventional removal of phosphorus from wastewater, but the process is poorly investigated. This study examined the effect of biofilm thickness on the activity and microbial diversity of phosphorus-accumulating bacteria. Biofilms of 30 to 1000 µm were grown on 5 different carriers in a moving bed biofilm reactor. Measurements on each type of carrier showed that biomass-specific phosphorus release and uptake rates increased as a function of biofilm thickness for biofilms thinner than about 110 µm but were lower for thicker biofilms of about 550-1000µm. On the other hand, anaerobic acetate consumption rates were rather similar for the thinner but decreased for the thicker biofilms. The reduced phosphorus uptake and release rates in the thickest biofilms can result from substrate mass transfer limitations whereas the low activity in the thinnest biofilms can be related to a too high turnover rate in the biofilm due to heterotrophic growth.