The pollutants diffuse through the biofilm due to the concentration difference. In conventional biofilms oxygen comes from the water and is consumed in the outer layers of the biofilm. In the OxyMem MABR the oxygen is supplied to the base of the biofilm. The pollutants still need to diffuse into the biofilm to be consumed. Some are degraded in the outer layers (which) are anoxic. While others including ammonia diffuse to the aerobic layer at the base of the biofilm. Please see the corresponding image
In BNR (Biological Nutrient Removal) systems the functional groups of nitrifiers and heterotrophs co-exist in the system. Can heterotrophs out-compete nitrifiers in biofilm in high organic carbon environments?
No, the Membrane Aerated Biofilm Reactor is a more balanced ecosystem. The nitrifiers are located at the base of the biofilm attached to the membrane surface, not at the surface as in other biofilm system, this means that they are protected from sloughing and erosion. The hetrotrophic bacteria grow in the outside layer where they have plenty of organic carbon and utilise nitrate and any excess oxygen that diffuses through the nitrifying layer. Please see the corresponding images .