Studies on the removal of nitrogen constituents by a dual media expanded bed bioreactor showed substantial removals of about 85% COD and 80% total-N. Kinetic parameters obtained were: for growth, Y-H = 0.23 mg/mg, mu(H) = 0.278 day-1, K-H = 461 mg/L and b(H) = 0.0151 day-1 and for denitrification, Y-HD = 0.670 mg/mg, mu(HD) = 0.205 day-1, K-HD = 0.54 mg/L and b(HD) = 0.0300 day-1. Hydrodynamics studies gave U-t (terminal settling velocity) and U-mf (minimum fluidization velocity) for bare GAC as 0.637 m/s and 0.005 m/s respectively. For GAC with biofilm, U-t was at 0.426-0.083 m/s, with almost double the increase in buoyancy for particles carrying biofilm. This in turn reduced the U-mf for GAC with biofilm, which was at 0.0062-0.0009 m/s.