Monday, April 30, 2007

The effect of the surfactants on the estimation bacterial density in petroleum samples

Aderval S. Luna, Antonio Carlos A. da Costa, Marcia Monteiro M. Gonçalves, and Kelly Yaeko M. de Almeida. Programa de Pós-graduação em Engenharia Quimica, Universidade do Estado do Rio de Janeiro - Instituto de Quimica, Rua São Francisco Xavier, 524 - PHLC - sala 310, Rio de Janeiro, 20559900, Brazil

The effect of the surfactants polyoxyethylene sorbitan monooleate (Tween 80), cetyl trimethyl ammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) on the estimation of bacterial density (sulfate-reducing bacteria - SBR and General Anaerobic Bacteria - GAnB) was examined in the petroleum samples.  In order to carry out the experiments, we selected three different mixtures of oil and water to be representative of the real samples. The first one contains a high proportion of oil, the second contains a medium proportion and the last one contains a low proportion. The most probable number (MPN) was used to estimate the bacterial density. The concentrations of the surfactants used in this work were determined in a previous study. The results showed that a viable count of GAnB was significantly improved when Tween 80 was added in the medium. In opposite, the estimation of bacterial density for SBR did not show difference in the presence or absence of the surfactant. The other surfactants showed an inhibit effect or, at least, similar results when no surfactants were used.