Biological nutrient removal (BNR) is a wastewater treatment process that uses microorganisms to remove excess nutrients, primarily nitrogen and phosphorus, from sewage. This process helps prevent water pollution and promotes environmental sustainability by reducing nutrient loads that can lead to harmful algal blooms in water bodies. In BNR systems, specific bacteria are cultivated to convert nitrogen compounds into harmless nitrogen gas, which is released into the atmosphere. Additionally, other microorganisms uptake phosphorus, allowing it to be removed from the water. Effective BNR contributes to cleaner water and supports the health of ecosystems, making it a vital component of modern wastewater treatment facilities.