Wastewater Treatment : The wastewater to be treat is introduce into the MBBR reactor. The biofilm carriers in the reactor provide a habitat for the microorganisms involve in the treatment process.
Biofilm Formation: Over time, the microorganisms in the wastewater start to attach themselves to the biofilm carriers, forming a layer of biofilm. The biofilm consists of bacteria, fungi, and other microorganisms that are capable of degrading organic pollutants.
Suspended Growth: In addition to the attache growth on the biofilm carriers, there is also a population of suspend microorganisms in the wastewater. These suspend microorganisms contribute to the biological treatment process by metabolizing organic matter.
Aeration and Mixing: The MBBR system is equippe with diffusers or mechanical mixers to provide aeration and mixing within the reactor. The aeration supplies oxygen to support the metabolic activities of the microorganisms, while the mixing ensures proper contact between the wastewater and the biofilm carriers.
Biological Degradation: The microorganisms in the biofilm and the suspend growth utilize the organic matter in the wastewater as a food source. They break down the organic compounds through biological degradation, converting them into simpler compounds, such as carbon dioxide and water.
Settling and Clarification: After the biological treatment stage, the treat wastewater undergoes settling and clarification processes to separate the biomass (biofilm carriers and excess microorganisms) from the treat water. The clarifie water, or effluent, is then discharge or subject to further treatment if necessary.
Biomass Retention: A portion of the biomass, including biofilm carriers and microorganisms, is recycle back to the reactor to maintain the desire microbial population and ensure continuous treatment. This is known as the return activate sludge (RAS) or the return sludge.

The process is widely use in municipal wastewater treatment plants and industrial facilities to treat domestic sewage and various types of industrial wastewater. It is known for its efficiency, versatility, and ability to handle varying influent characteristics.