Affiliations: Instituto de Ingeniería, Universidad Nacional
Autó noma de México, Coordinación de Ingeniería
Ambiental, Grupo Saneamiento de Suelos y Acuíferos, Apartado Postal
70–472, Coyoacán 04510, México, D.F. Mexico
Abstract: In a surfactant assisted biodegradation process, the choice of
surfactant(s) is of crucial importance. The question is: does the type of
surfactant (i.e. chemical family) affect the biodegradation process at fixed
hidrophillic-lypofillic balance HLB values? Microcosm assessments were
developed using contaminated soil, with around of 5000 mg/kg of hydrocarbons as
TPH-diesel. Mixtures of three nonionic surfactants were employed to get a wide
range of specific HLB values. Tween20 and Span20 were mixed in the appropriate
proportions to get HLB values between 8.6 and 16.7. Tween/Span60 mixtures
reached HLB values between 4.7 and 14.9. Finally, Tween/Span80 combinations
yielded HLB values between 4.3 and 15. TPH-diesel biodegradation was measured
at the beginning, and after 8 weeks, as well as the
FCU/gr_{soil}, as a measure of microorganisms' development
during the biodegradation period. A second aim of this work was to assess the
use of guar gum as a biodegradation enhancer instead of synthetic products. The
conclusions of this work are that surfactant chemical family, and not only the
HLB value clearly affects the assisted biodegradation rate. Surfactant's
synergism was clearly observed. Regarding the use of guar gum, no
biodegradation enhancement was observed for the three assessed concentrations.
i.e., 2, 20, and 200 mg/kg, respectively. On the contrary, TPH-diesel removal
was lower as the gum concentration increased. It is quite possible that guar
gum was used as a microbial substrate.
