The aim of this work was to study the oleic acid degradation in anaerobic filters, evaluating both the
effects of using an acclimatized inoculum and biomass recirculation. The anaerobic filters (R1, R2 e R3)
were operated in parallel. In R1 and R2 the inoculated biomass was not acclimatized while in R3 it was. On
the other hand in R2 and R3 biomass recirculation was used while in R1 it was not.
Filters performance was followed during 233 days and evaluated in terms of soluble COD (Chemical
Organic Demand) removal, VFA (Volatile Fatty Acids) and VSS (Volatile Suspense Solids) in the outlet, and
methane production. Removal efficiencies between 70 and 77% were achieved for an oleate organic load of
12.5 kgCOD/m3.day, even with an oleate/(...) molar concentration ratio of 6.79. While following
methane production it was possible to observe an effective degradation of the fed oleate. Nevertheless, a
significative difference was found between soluble COD removal and methane production, suggesting that
most of the oleate fed would beretained in the reactor.
Biomass recirculation was found to enhance the system performance, due to biomass washout
minimization and dilution of the toxic organic load, inducing a lower inhibition on the acetogenic and
metanogenic populations. Sodium oleate inhibitory effect on both acetogenic and metanogenic populations
was lower in an anaerobic filter inoculated with biomass acclimatized with lipids and oleate. It was
concluded that the synergic effect of using biomass recirculation and an acclimatized inoculum is beneficial,
when treating effluents hardly loaded with oleate, improving the performance of the anaerobic filter.
Final characterization of the biomass developed in the filters showed that the contact with oleate
induced a significant decrease of methanogenic activity against acetate and ethanol and an enhancement
against H2/CO2. Acclimatized biomass exhibited a higher capacity to develop hidrogenofilic activity when in
contact with oleate.
When oleate was the sole carbon source fed, biomass became encapsulated, probably due to oleate
adsorption, inducing a significative delay on added oleate degradation. The experiment run in the reactor, in
the absence of feed, showed that the degradation to methane of the oleate adsorbed during continuous
operation was efficient. This put in evidence the potential use of adsortion/degradation cycles in the
treatment oleate hardly loaded effluents.
Publication Type: MSc Dissertations