INFLUENCE OF REACTOR TYPE AND SHEAR-STRESS ON AEROBIC BIOFILM MORPHOLOGY, POPULATION AND KINETICS

The influence of flow pattern on the microbial community of biofilm sy stems is relevant for process analysis, reactor selection and microbia l ecology control. The interaction between reactor type, shear stress, microbial population, intrinsic kinetics, and biofilm performance for biofilm systems was studied by comparing experimental results of thre e reactors: a batch reactor representing plug flow, and a CSTR and an indoor channel reactor with recirculation, two configurations of conti nuous stirred tank reactors but with different shear stress. Cocci co- existed with filaments (mainly Sphaerotilus natans) in the batch react or biofilm, whereas filaments predominated in the other two reactors. The values of the Monod constants mu(max) and K-s of the biofilm bioma ss of the batch reactor were 2.8 day(-1) and 54 mg(glucose)/l at 28 de grees C, whereas in the CSTR and channel they were 1.3 day(-1) and 2.9 mg/l, and 1.5 day(-1) and 2.7 mg/l, respectively. The oxygen consumpt ion coefficients of biofilm decreased from 50 to 10% (gO(2)/gglu), whe n biofilm surface loading increased from 50 to 400 gglu/m(2).day in th e CSTR and channel reactors. An analogy was found between intrinsic mi crobial kinetics and the corresponding macroscopic biofilm kinetics. A conceptual model of these interactions was proposed.