The main function of denitrifying bacteria is to reduce nitrite in water and transform it into harmless nitrogen, thus eliminating the harm of nitrite. These bacteria can also improve the eutrophic water body and further purify the water quality by decomposing organic matter.

Bacillus subtilis can secrete a variety of extracellular enzymes with high activity, such as protease, amylase, hemicellulose hydrolase, etc., and can decompose and absorb organic substances in the water environment, which is helpful to improve water quality. In addition, Bacillus subtilis can also interact with denitrifying bacteria to further improve the effect of sewage treatment.

To sum up, denitrifying bacteria and Bacillus subtilis have practical effectiveness in sewage treatment, especially in the degradation of nitrite and organic waste. However, the specific treatment effect will be affected by many factors, such as the type and quantity of bacteria, the degree of water pollution, environmental conditions and so on. Therefore, in practical application, it is necessary to reasonably select and optimize the treatment process according to the specific situation.