What type of bacteria are primarily responsible for the nitrification process in wastewater treatment?

The nitrification process in wastewater treatment is primarily conducted by specialized groups of bacteria, particularly Nitrosomonas and Nitrobacter. These bacteria play a crucial role in converting ammonia into nitrites and then into nitrates, two key steps in the nitrogen cycle.

Nitrosomonas is responsible for the oxidation of ammonia (NH3) into nitrite (NO2-), and this process is critical because ammonia is toxic to aquatic life. Following this, Nitrobacter takes the nitrite produced by Nitrosomonas and converts it into nitrate (NO3-). This two-step process is vital for both the treatment of wastewater and for minimizing the environmental impact of nitrogen compounds released into water bodies.

The other choices represent bacteria that are involved in different processes. Clostridium is primarily associated with fermentation processes and anaerobic digestion. Escherichia coli is a coliform bacterium often used as an indicator of fecal contamination rather than a participant in nitrification. Streptococcus primarily contributes to the fermentation of carbohydrates and does not play a role in nitrification either. Therefore, Nitrosomonas and Nitrobacter are the correct answer, as they are directly involved in the nitrification process, ensuring the effective removal of ammonia from wastewater.