Morphological examination of nitrifying biofilms in a moving bed biofilm reactor using optical coherence tomography and fluorescence in situ hybridization

We present an imaging and image analysis approach to quantify both the overall morphology and the spatial distribution of nitrifying guilds in mixed-culture, nitrifying biofilms enriched on K1 carriers. For image acquisition we used optical coherence tomography to non-destructively visualize the three dimensional structure of entire internal cavities and fluorescent in situ hybridization of carrier cryosections to visualize the spatial distribution of ammonia oxidizing bacteria and nitrite oxidizing relative to the overall biofilm structure. Determination of morphological parameters relies on the adaptation of current image analysis methods to accommodate the complex, curved geometry of MBBR carriers.