In water, nitrogen exists in form of organic nitrogen, ammonia nitrogen, nitrite and nitrate.

From another point of view, our study tries to find a potential of heterotrophic nitrification for the improvement of contaminated aquatic environment.

Analysis shows that more nitrogen is oxidized by ammonia oxidizing bacteria(AOB) than by nitrite oxidizing bacteria(NOB) with more growth of the AOB than the NOB in each cycle when using this method.