Biofilm reactors are specialized systems used in wastewater treatment and bioprocessing. They utilize biofilms, which are layers of microorganisms that attach to surfaces, to break down organic matter and pollutants. The design of these reactors allows for efficient mass transfer and nutrient exchange, enhancing the growth of beneficial microbes. These reactors can vary in design, including fixed-bed, moving-bed, and fluidized-bed configurations. Each type offers unique advantages in terms of space efficiency and treatment capacity. Biofilm reactors are widely used in industries such as food processing, pharmaceuticals, and environmental engineering to improve water quality and reduce environmental impact.