C. Nicolella et al., TERMINAL SETTLING VELOCITY AND BED-EXPANSION CHARACTERISTICS OF BIOFILM-COATED PARTICLES, Biotechnology and bioengineering, 62(1), 1999, pp. 62-70
Fluid dynamic behavior of biofilm-coated particles in ambient water ha
s been investigated. New experimental results are presented and compar
ed with published data. From experimental measurements of the single p
article terminal settling velocity the corresponding drag coefficient
was found to be larger (by a factor of 1.6) than that for a smooth, ri
gid sphere at the same Reynolds number. A new simple correlation descr
ibing this finding is suggested. For multiparticle systems the Richard
son-Zaki equation, derived empirically for rigid particles, provided a
satisfactory description of biological beds. Of the two numerical par
ameters characterizing the expansion law, i.e. the slope n and the ext
rapolation to voidage equal one u(i), the first was found to be simila
r to that suggested by Richardson and Zaki (1954), whereas u(i) gave r
esults smaller than the single-particle terminal settling velocity, in
contrast with the mentioned work but in agreement with more recently
published behavior. (C) 1999 John Wiley & Sons, Inc. Biotechnol Bioeng
62: 62-70, 1999.