How Low Temperatures Affect Sewage Treatment Biofilms

In cities, sewage treatment plants use unique reactors with moving bed biofilms to clean wastewater. These reactors rely on microbes to break down the waste. Scientists studied how cold temperatures impact these microbes. They found that when it gets cold, the quality of the treated water decreases. The main types of microbes are Proteobacteria, Bacteroidota, and Nitrospirota. At a more detailed level, Gammaproteobacteria, Alphaproteobacteria, and Bacteroidia are the most common. As the temperature drops, the mix of microbes starts to look similar across different zones. Pseudomonas thrives at 5°C (41°F). Two types of microbes—Nitrospira and Trichococcus—show a link to ammonia nitrogen levels and nitrate production in the cold. Most of these microbes focus on decomposing organic matter, not just changing ammonia into nitrate. This means even though low temps slow some bacteria, others can still handle the waste.