Abstract
Factors affecting the performance of ammonia removal by ozone under the existence of bromide were investigated. Under the existence of bromide, both the reactions of nitrogen gas formation (TN removal) and nitrate formation were found to be in near zero-order kinetics with respect to ammonia concentration. The nitrogen gas formation rate increased linearly with the increase of initial bromide concentration, while the nitrate formation rate was decreased by the increase of initial bromide concentration. In addition to the initial bromide concentration, the ratio of Br to N (NH4+-N) was also found to be an important parameter in controlling nitrate formation : nitrate formation rate decreased with increasing the Br/N ratio. In the pH range of 4 to 9, the nitrate formation rate increased with the increase of pH, while a maximum nitrogen gas formation rate existed around pH 6. From the view points of reaction rate and nitrate formation control, the optimum pH value was around 6. The nitrogen gas formation rate increased by 50% when temperature was increased from 13 to 39°C, while the nitrate formation rate remained constant. ORP (oxidation-reduction potential) showed an instant response when ammonia was completely removed, and therefore was considered to be an effective parameter for process control.
