RELAXATION-TIME ANALYSIS OF A ROTATING BIOLOGICAL CONTACTOR

The present work is aimed to use the ''relaxation time approach'' in o rder to ascertain the main parameters affecting the steady state behav iour of a Rotating Biological Contactor (RBC). A large concentration r ange of surfactant was experimentally tested at different rotational s peed and substrate load in aerobic conditions. Hydraulic residence tim e and time constants (relaxation time) relative to the following mecha nisms were estimated: substrates and oxygen uptake and mass transfer; mixing effects as a consequence of discs rotation. Substrate uptake ra te and biodegradation efficiency are considered as probe parameters fo r the RBC performances. Time constants of different phenomena are comp ared and discussed considering operational parameters such as rotation al Reynolds number and specific substrate load. Biomass characteristic s are taken into account by considering two morphological classes for biofilm. The mapping of bottleneck phenomena on operational parameters is set-up, analysed and commented.