Toluene biodegradation in an algal-bacterial airlift photobioreactor: Influence of the biomass concentration and of the presence of an organic phase.
The potential of algal-bacterial symbiosis for off-gas abatement was investigated for the first time by comparatively evaluating the performance of a bacterial (CB) and an algal-bacterial (PB) airlift bioreactors during the treatment of a 6 g m-3toluene laden air emission. The influence of biomass concentration and of the addition of a non-aqueous phase was also investigated. A poor and fluctuating performance was recorded during the initial stages of the experiment, which was attributed to the low biomass concentration present in both reactors and to the accumulation of toxic metabolites. In this sense, an increase in the dilution rate from 0.23 to 0.45 d-1and in biomass concentration from ∼1 to ∼5 g L-1resulted in elimination capacities (ECs) of 300 g m-3h-1(corresponding to removal efficiencies ∼ 90%). Microalgae activity allowed for a reduction in the emitted CO2and an increase in dissolved O2concentration in the PB. However, excess biomass growth over 11 g L-1hindered light penetration and severely decreased photosynthetic activity. The addition of silicone oil at 20% (on a volume basis) stabilized system performance, leading to dissolved O2concentrations of 7 mg L-1and steady ECs of 320 g m-3h-1in the PB. The ECs here recorded were considerably higher than those previously reported in toluene-degrading bioreactors. Finally, microbial population analysis by DGGE-sequencing demonstrated the differential specialization of the microbial community in both reactors, likely resulting in different toluene degradation pathways and metabolites production.
Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina, s/n, 47011, Valladolid, Spain. Electronic address: raquel.lebrero@iq.uva.es.
Raquel
R
Lebrero
Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina, s/n, 47011, Valladolid, Spain.
Roxana
R
Ángeles
Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina, s/n, 47011, Valladolid, Spain.
Rebeca
R
Pérez
Department of Chemical Engineering and Environmental Technology, University of Valladolid, Dr. Mergelina, s/n, 47011, Valladolid, Spain.
Raúl
R
Muñoz
D000393:Air Pollutants / Q000378:metabolism*; D000397:Air Pollution; D001673:Biodegradation, Environmental; D018533:Biomass; D002708:Chlorella / Q000378:metabolism*; D058086:Microalgae / Q000378:metabolism*; D058433:Photobioreactors / Q000382:microbiology*; D016958:Pseudomonas putida / Q000378:metabolism*; D014050:Toluene / Q000378:metabolism*
D000393:Air Pollutants; D014050:Toluene
Airlift bioreactor; Algal-bacterial photobioreactor; Toluene biodegradation; Two-phase partitioning bioreactor