In wastewater treatment, what does 'nitrification' refer to?

Nitrification is specifically the biological process where ammonia is converted into nitrate. This process typically occurs through two steps involving different types of bacteria: first, ammonia-oxidizing bacteria convert ammonia to nitrite, and then nitrite-oxidizing bacteria further convert nitrite to nitrate. Nitrification is essential in wastewater treatment as it helps reduce ammonia levels, which can be toxic to aquatic life and can lead to water quality issues.

The other options do not accurately describe nitrification. The removal of phosphates pertains to a different chemical process known as phosphorus removal, while the breakdown of organic matter is more aligned with processes like aerobic or anaerobic digestion. Lastly, filtering wastewater encompasses physical treatment processes and is unrelated to the specific biochemical transformations that occur during nitrification.