Autotrophic nitrogen-removing biofilms on porous and non-porous membranes.

The effective removal of nitrogen compounds from wastewater has become a critical issue for treatment plants as the awareness of their negative impact on the environment increased. Autotrophic nitrogen removal has become an interesting alternative to the more conventional heterotrophic processes, as it eliminates the need for an organic carbon addition to the source water and reduces biomass yields. Gas transfer membrane biofilm reactors (MBfR) for nitrification and hydrogen driven denitrification are of special interest as they combine membrane diffusers and biofilms, provide an efficient supply of necessary electron donor for autotrophic removal of ammonia and nitrate, extend solids retention times and retain biomass within the reactor. Subsequently, a wide range of MBfR, which vary based on the type of membrane material and membrane module configuration, are being tested for this purpose. This paper reviews the research to date and also discusses the challenges that still lay ahead before MBfR can be used at treatment plants.