Microbes have important effects on their environment. For example, the microbes used in AST are important in oxidizing ammonia to nitrite and then reducing nitrite to nitrogen gas. This reduces the nitrogen content of the water that could otherwise stimulate unwanted microbial growth. Other microbes have different effects on their environment and understanding these is important to protecting human structures as well as using bacteria for processes such as AST. During conventional wastewater treatment, bacteria are also used to reduce the amount of organic and inorganic materials so that the water no longer supports substantial microbial growth. During secondary wastewater treatment, bacteria within sludge digesters break down organic materials into fatty acids H2 and CO2. These products are fermented to acetate, CO2 and H2. Finally, archaeans ferment acetate to form methane and carbon dioxide. Just by knowing this information, what is true of the bacteria used in sludge digesters