Nitrifying activity monitoring and kinetic parameters determination in a biofilm airlift reactor by respirometry

The applicability of batch respirometry, as a simple technique for monitoring off-line nitrifying activity and kinetic parameters, was evaluated using two sets of ammonia and nitrite concentrations. The O₂ uptake rate (OUR) profiles obtained from the assays were adjusted to a substrate inhibition model. The maximum specific ammonia-oxidizing biomass activity (r_Smax) was 0.079 g N-NH₄⁺ g VSS^-1 d^-1 with a half saturation coefficient (K_s) of 11 mg NNH₄⁺ 1^-1 and an inhibition coefficient (K_i) of 3300 mg N-NH⁴⁺ 1^-1. Besides, the maximum specific value of nitrite-oxidizing activity was 0.082 g N-NO₂^- g VSS^-1 d^-1 with a K_s of 4.1 mg N-NO₂^-1^-1and K_i of 1400 mg N-NO₂^- 1^-1.