The term in parentheses is the effective Henry’s law constant, H. It depends
inversely upon the air bubble size.
11.2.6 Airlift Reactors (ALRs)
ALRs have proved to be efficient alternative devices against conventional systems
such as stirred tanks and bubble column contactors for the remediation of several
antibiotic-contaminated water bodies, even more because their applications range
from synthesis of chemicals, culture of plant and animal cells, production of
microalgae, fuel gas and contaminated soils. These are cylindrical or rectangular
vessel with a gas distributor at the inlet, usually without mechanical moving parts
(Fig. 11.3) (Huang and McDonald 2009). The only energy input needed is to inject
the aeration gas through a simple sparging system (Brenner et al. 1997). ALRs are
considered as feasible and sustainable alternatives for stirred tank reactors (STRs),
particularly for numerous bioprocesses such as plant and animal cell cultures but also
for the treatment of contaminated fluid fluxes (Benyahia and Jones 1997).
The volumetric mass transfer coefficient (k L a) is the rate of gas transfer across the
gas-liquid interface per unit of driving force (the driving force is the gas
Fig. 11.3 Airlift reactor for
wastewater and effluent
treatment
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A. S. Gupta et al.