Janez Vrtovšek*, Milenko Roš*
*National Institute of Chemistry, PO BOX 660, Hajdrihova 19, SI-1001 Ljubljana,
This study demonstrated the feasibility of a fixed-bed reactor system with a specific biomass support material for groundwater treatment. The denitrification rate increased up to a maximal value of 1.3 gNO3-N·m-2·day-1 with increasing nitrogen loading rate. Kinetic analysis of the system confirmed a half-order denitrification kinetic region in the NOx-N concentration range from 0.25 mg·L-1 to 16 mg·L-1, with the half-order reaction coefficient k1/2 of 0.35 g0.5·m-0.5·day-1 when the carbon source was in excess. Under the experimental conditions, drinking water quality was achieved at a nitrogen loading lower than 1.9 g NO3-N·m-2·day-1 with an influent COD/N ratio of 3.7 if acetate was used as the carbon source. The system is fairly robust; it can be operated in a simple manner at low hydraulic loadings without recirculation flow and without backwashing.
Key words: biofilm reactor, denitrification, external carbon substrate, groundwater, kinetics