At
least three conceptual models of biofilm structure exist: the
heterogeneous mosaic model, the water-channel model and
the dense biofilm model, according to substrate concentration
(19). In this study, the biofilm structure and its bacterial
composition varied during the bioreactor operation (Fig. 2a,
b), displaying heterogenic channelled forms (the water-channel
model) as described by Beer and Stoodley (20)