Study of variation in droplet size of an aqueous-diesel emulsion formed by an oil-degrading microbial consortium

The variation in droplet size as a function of superficial air velocity (0.2, 0.4 and 0.8 cm s−1) and culture time (10 days) for the biodegradation of diesel by a microbial consortium has been studied in a bubble column bioreactor. With respect to superficial air velocity, the Analysis of Variance ANOVA (at a significance level of α = 0.01) showed that for larger droplet sizes (around 600 nm) the culture time had no influence over the size of the droplets, whereas the air superficial velocity can be accounted as an important factor. However, for smaller droplet sizes (lower than 300 nm) the analysis showed that the culture time had no influence when operating the bioreactor exclusively at air velocities 0.4 and 0.8 cm s−1 but for the case of 0.2 cm s−1 the statistical analysis detected significant differences in the case of culture time. The results indicated that the microbial consortium is needed to produce surfactants, to create oil micro emulsions. This study suggests that a further insight into mass transfer mechanisms, diesel-biodegradation and operating conditions are needed to establish the optimal diesel degradation by microbial consortia in a bubble column bioreactor.