Long-chain fatty acids (LCFA) associated with
anaerobic sludge by mechanisms of precipitation, adsorption, or entrapment can be biodegraded to methane. The mineralization kinetics of biomass-associated LCFA were established according to an inhibition model based on Haldane’s enzymatic inhibition kinetics. A value around
1,000 mg COD-LCFA g VSS-1 was obtained for the optimal specific LCFA content that allowed the maximal mineralization rate. For sludge with specific LCFA contents of 2838 ± 63 and 4571 ± 257 mg COD-LCFA g VSS-1, the specific methanogenic activities in the presence of
acetate, butyrate, and H2/CO2 were significantly enhanced
after the mineralization of the biomass-associated LCFA.
For sludge with a specific LCFA content near the optimal
value defined by the kinetic model, the effect of adding
VFA to the medium was studied during the mineralization
of the biomass-associated LCFA. Different patterns were
obtained for each individual substrate. Acetate and butyrate
were preferentially consumed by the consortium, but
in the case of propionate no evidence of a sequential consumption
pattern could be withdrawn. It was concluded
that LCFA do not exert a bactericidal neither a permanent
toxic effect toward the anaerobic consortia. A discussion is
addressed to the relative roles of a reversible inhibitory effect
and a transport limitation effect imposed by the LCFA
surrounding the cells.Fundação para a Ciência e Tecnologia (FCT) - PRAXIS XXI/BD/20326/99, SFRH/BD/8726/2002.
Fundo Social Europeu (FSE)
