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Influence of biomass production and detachment forces on biofilm structures in a biofilm airlift suspension reactor
Author(s) -
Kwok W. K.,
Picioreanu C.,
Ong S. L.,
van Loosdrecht M. C. M.,
Ng W. J.,
Heijnen J. J.
Publication year - 1998
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/(sici)1097-0290(19980520)58:4<400::aid-bit7>3.0.co;2-n
Subject(s) - biofilm , biomass (ecology) , airlift , substrate (aquarium) , yield (engineering) , chemistry , suspension (topology) , extracellular polymeric substance , chemical engineering , bioreactor , materials science , composite material , biology , ecology , bacteria , genetics , organic chemistry , homotopy , pure mathematics , engineering , mathematics
The influence of process conditions (substrate loading rate and detachment force) on the structure of biofilms grown on basalt particles in a Biofilm Airlift Suspension (BAS) reactor was studied. The structure of the biofilms (density, surface shape, and thickness) and microbial characteristics (biomass yield) were investigated at substrate loading rates of 5, 10, 15, and 20 kg COD/m 3 · day with basalt concentrations of 60 g/L, 150 g/L, and 250 g/L. The basalt concentration determines the number of biofilm particles in steady state, which is the main determining factor for the biofilm detachment in these systems. In total, 12 experimental runs were performed. A high biofilm density (up to 67 g/L) and a high biomass concentration was observed at high detachment forces. The higher biomass content is associated with a lower biomass substrate loading rate and therefore with a lower biomass yield (from 0.4 down to 0.12 g biomass /g acetate ). Contrary to general beliefs, the observed biomass detachment decreased with increasing detachment force. In addition, smoother (fewer protuberances), denser and thinner compact biofilms were obtained when the biomass surface production rate decreased and/or the detachment force increased. These observations confirmed a hypothesis, postulated earlier by Van Loosdrecht et al. (1995b), that the balance between biofilm substrate surface loading (proportional to biomass surface production rate, when biomass yield is constant) and detachment force determines the biofilm structure. When detachment forces are relatively high only a patchy biofilm will develop, whereas at low detachment forces, the biofilm becomes highly heterogeneous with many pores and protuberances. With the right balance, smooth, dense and stable biofilms can be obtained. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 58:400–407, 1998.