A TECHNIQUE TO DETERMINE THE SIMULTANEOUS NITRIFICATION AND DENITRIFICATION RATES IN AN INTERMITTENT AERATION TANK

This paper reports on a technique to determine potential specific nitrification and denitrification rates (SNR and SDNR) in an oxidation-reduction potential (ORP) controlled, intermittent aeration (IA) tank, in which nitrification and denitrification occurred simultaneously. In addition, potential SNRs in the aerobic zone of a three-stage (anaerobic, anoxic and oxic) and potential SDNRs in its anoxic zone were determined using this technique. The technique involves a steady-state run and two additional transient-state phases: one created by ammonia shock loading and the other by nitrate shock loading. The technique is flexible and generates data relating rate to substrate concentration in one steady-state run. Data analysis was performed using the integral method; an excellent agreement between predicted and experimental data was found. Zero-order kinetics could describe nitrification in an ammonia concentration range of 10-30 mgN/L and denitrification in a nitrate concentration range of 10-30 mgN/L. The potential SNRs in the IACM tank (0.39-1.69 mgNH+ 4-N/gMLVSS h−1) were considerably lower than those in the aerobic zone of the three-stage process (3.4-8.1 mgNH+ 4-N/gMLVSS h−1); the potential SDNRs in the IACM tank were in a range of 0.16-1.26 mgNOx-N/gMLVSS h−1, which were also considerably lower than that in the anoxic zone of the three-stage process (2.5 mgNOx-N/gMLVSS h−1).