Biological denitrification of drinking water using autotrophic organisms with H 2 in a fluidized‐bed biofilm reactor

Biological denitrification of drinking water was studied in a fluidized sand bed reactor using a mixed culture. Hydrogen gas was used as the reaction partner. The reaction kinetics were calculated with a double Monod saturation function. The K s value for hydrogen was below 0.1% of saturation. No appreciable biofilm diffusion effects were detected. Reactor performance was a function of the culture's past history. Batch experiments always exhibited an accumulation of NO 2 − , but continuous experiments with a sufficiently long residence time always resulted in complete nitrogen removal. Rates of up to 23 mg N/L h, 25 mg N/g DW h, and 7.9 mg H 2 /L h were achieved. Residence times of 4.5 h would be required for complete denitrification of water containing 25 mg NO 3 − –N/L or approximately 1 h for every 5 mg/L.