Groundwater denitrification was carried out in a fluidized bed reactor
. This type of reactor is suited well to conditions of low substrate c
oncentrations and high flow rates which are typical in groundwater den
itrification processes. The reactor is characterized by the efficient
contact between biomass and substrate, a high biomass concentration, a
nd the absence of clogging or channeling. These characteristics provid
e for high treatment capacities (10.8 g/(L.d) NO3--N) and short retent
ion times (less than 3 minutes) resulting in small reactor volume. Sta
rt-up procedure, biomass and nitrate profiles, and biofilm characteris
tics are presented in this article.