Biodegradation of airborne acetone/styrene mixtures in a bubble column reactor

• Published in: Journal of environmental science and health. Part A, Toxic/hazardous substances & environmental engineering Vol. 52; no. 9; pp. 905 - 915
• Main Authors: Vanek, T., Silva, A., Halecky, M., Paca, J., Ruzickova, I., Kozliak, E., Jones, K.
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 29.07.2017; Taylor & Francis Ltd
• Subjects: Accumulation; Acetone; Acetone - analysis; Activated sludge; Aerobiosis; Air flow; Air Pollutants - analysis; Air pollution; Biodegradation; Biodegradation, Environmental; Biomass; Bioreactors - microbiology; bubble column reactor; Bubble columns; Bubbles; Degradation; Dissolved oxygen; Filtration - methods; Guanylate cyclase; Intermediates; Kinetics; Limiting factors; Load distribution; Loading rate; Mass transfer; Microorganisms; Nematodes; Organic loading; Oxygen; Pollutant removal; Pollutants; Reaction kinetics; Reactors; Sewage - microbiology; Styrene; Styrene - analysis; Vapors; waste air treatment; waste air treatment; biodegradation; bubble column reactor; intermediates; Acetone; styrene
• ISSN: 1093-4529; 1532-4117
• DOI: 10.1080/10934529.2017.1318629

The ability of a bubble column reactor (BCR) to biodegrade a mixture of styrene and acetone vapors was evaluated to determine the factors limiting the process efficiency, with a particular emphasis on the presence of degradation intermediates and oxygen levels. The results obtained under varied loadings and ratios were matched with the dissolved oxygen levels and kinetics of oxygen mass transfer, which was assessed by determination of k L a coefficients. A 1.5-L laboratory-scale BCR was operated under a constant air flow of 1.0 L.min −1 , using a defined mixed microbial population as a biocatalyst. Maximum values of elimination capacities/maximum overall specific degradation rates of 75.5 gC.m −3 .h −1 /0.197 gC.gdw −1 .h −1 , 66.0 gC.m −3 .h −1 /0.059 gC.gdw −1 .h −1 , and 45.8 gC.m −3 .h −1 /0.027 gC.gdw −1 .h −1 were observed for styrene/acetone 2:1, styrene-rich and acetone-rich mixtures, respectively, indicating significant substrate interactions and rate limitation by biological factors. The BCR removed both acetone and styrene near-quantitatively up to a relatively high organic load of 50 g.m −3 .h −1 . From this point, the removal efficiencies declined under increasing loading rates, accompanied by a significant drop in the dissolved oxygen concentration, showing a process transition to oxygen-limited conditions. However, the relatively efficient pollutant removal from air continued, due to significant oxygen mass transfer, up to a threshold loading rate when the accumulation of acetone and degradation intermediates in the aqueous medium became significant. These observations demonstrate that oxygen availability is the limiting factor for efficient pollutant degradation and that accumulation of intermediates may serve as an indicator of oxygen limitation. Microbial (activated sludge) analyses revealed the presence of amoebae and active nematodes that were not affected by variations in operational conditions.