The process of converting nitrate to nitrogen gas is called [[1]]. 

Denitrification is the process of converting nitrate to nitrogen gas. This process plays a critical role in removing harmful nitrates from domestic and industrial wastewater, helping to make it safer for release into the environment.

In sewage treatment, denitrification is a biological process used to remove nitrogen from wastewater.

During the process of denitrification in sewage treatment, specific bacteria are used to convert nitrate (NO3-) in the wastewater to nitrogen gas (N2). This is achieved by providing an anaerobic (oxygen-free) environment in which the bacteria can grow and carry out the denitrification process. Denitrification is often used in conjunction with other wastewater treatment processes, such as biological nutrient removal, to ensure that the levels of nitrogen and other nutrients in the wastewater are reduced to safe levels before it is discharged into the environment.