When communities of microorganisms grow on surfaces, they are called biofilms or biocarriers. Microorganisms in a biofilm wastewater treatment process are more resilient to process disturbances compared to other types of biological treatment processes. Thus, biofilm wastewater treatment technologies can be considerably more robust than other technologies.
Biocarriers are suspended in the wastewater of the reactor, and are in continuous movement within a tank or reactor of specified volume.
Biofilm, growing within the internal structures of the biocarriers, degrade dissolved pollutants in the waste water stream. The pollutants that need to be removed in order to treat the wastewater are food, dissolved sugars, or other various substrates, which contribute to the growth of the biofilm. The biocarrier design is critical due to requirements for efficient mass transfer of substrate and oxygen to the microorganisms in the area of the MBBR biofilm technology.
An aeration grid located at the bottom of the reactor supplies oxygen to the biofilm along with the mixing energy required to keep the biocarriers suspended and in constant mixing movement within the reactor.
Treated water flows from reactor, into a grid or a sieve. The purpose of this barrier is to retain the MBBR biocarriers within the reactor. Depending on the wastewater, the reactors may be equipped with special spray nozzles which prevent excessive foam formation.