Model based optimization of partial nitrification by monitoring nitrous oxide (N2O) emission

The successful operation of partial nitrification relies on the optimal condition in which the ammonia oxidizing bacteria (AOB) is favored over nitrite oxidizing bacteria (NOB). The fluctuation of influent load means the optimal condition varies dynamically. The routine monitoring such as dissolved oxygen (DO), nitrite and ammonia concentration is usually used for the system optimization. The sensors used for these routine monitoring are usually submerged in a hostile activated sludge environment and are subjected to sensor fouling. In this paper, the non-invasive off-gas nitrous oxide (N2O) monitoring was used for the optimization of partial nitrification. An empirical N2O emission model and a two-step nitrification activated sludge model No. 1 (ASM1) were used for the optimization study based on the concept of model predictive control. The results indicated that the non-invasive N2O monitoring can be used as an alternative to the nitrite and ammonia sensor for the optimization of partial nitrification process.