PILOT-PLANT EXPERIMENTS WITH MOVING-BED BIOFILM REACTORS

A flexible pilot plant, fed with primary settled wastewater, was used to study (1) organic carbon and nitrification in a two(three)-stage co ntinuous-flow aerobic process and (2) organic carbon and nitrogen remo val in a heterotrophic moving-bed sequencing batch biofilm reactor (MB SBBR) for denitrification and in a continuous-now autotrophic moving-b ed biofilm reactor (MBBR) for nitrification. In both experiments the s ame polyethylene biofilm carriers were used. Filtered COD removal rate s in aerobic conditions appear to be proportional to the corresponding loading rates up to 8 gCOD m(-2) d(-1). Nitrification tests, performe d in oxygen limiting conditions and ammonia limiting conditions, showe d that the reaction rate was nearly first order with respect to dissol ved oxygen due to liquid film diffusion. Denitrification tests,perform ed without external carbon sources, showed that the denitrification ra te never fell below 0.3 gNO(3)(-)-N m(-2) d(-1) even at very low biode gradable filtered COD loading rates. (C) 1997 IAWQ. Published by Elsev ier Science Ltd.