Biofilm reactors use bacteria to produce substances like vinegar, ethanol, and lactic acid, as well as for wastewater treatment. Different types include membrane, fluidized bed, packed bed, airlift, and upflow anaerobic sludge blanket reactors. Bacterial cells grow within a structural matrix and adhere to a surface, producing extracellular polymeric substances. Nutrients, temperature, and cell nature affect the quality of the reactor. Biofilm reactors can abate gases and odors and process large volumes of water or fluid at high speeds.
A biofilm reactor uses colonies of bacteria in laboratory and industrial processes to produce substances such as vinegar and acetic acid. It is also used to produce ethanol, lactic acid, butanol, fumaric acid and succinic acid. Biofilm is also used regularly for wastewater treatment and bacteria can adsorb or break down toxic substances in the water. The different types of biofilm reactors include membrane reactors, fluidized bed, packed bed, airlift, and upflow anaerobic sludge blanket reactors.
Within a biofilm reactor, bacterial cells grow within a structural matrix and adhere to a surface. Individual cells must first attach themselves to a surface, either by electrical charge or chemical attraction, or by the concentration of nutrients near this surface. Cells must be irreversibly attached to the surface to form a biofilm, which occurs when extracellular polymeric substances (EPS) are produced. Biofilms develop in the reactor when water channels form within them so that nutrients can reach underground areas. As nutrients are depleted, cells that focus on producing EPS break down the matrix for food and escape.
Nutrients, temperature and the nature of the cells affect the quality of a biofilm reactor. Membrane biofilm reactors, where the film grows on a gas transfer membrane, are one type. Bacteria use a gas-phase substrate, which can be hydrogen, oxygen or methane, ammonia or carbon dioxide. Contaminants, such as nitrates, nitrites, chlorates, bromate, arsenate, selenate and chloroform can be reduced to harmless products through this process.
The media is mechanically stirred in a continuously stirred tank reactor, but the mixture cannot be stirred when a film support structure is present. A packed bed reactor is first filled with support materials before bacteria are introduced and is fed bottom-up with nutrients. Bacterial cells tend to grow rapidly in this type of biofilm reactor. Upper bed reactors are fed from the top, but not all cells in the film receive the nutrients. Other reactors include fluidized bed, which is suitable for breaking down toxic phenolic chemicals, and aviation reactors, which mix air from the bottom with liquid in two tubes.
For water treatment, upflow anaerobic sludge blanket reactors treat wastewater and industrial effluents. A biofilm reactor can also be used to abate gases and odors. Overall, it can process large volumes of water or fluid at high speeds, creating an efficient industrial process.
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