Influence of Diphenyloxide Disulfonate Surfactants on Biodegradation of Hydrocarbons

Testing was conducted with anionic diphenyloxide disulfonate (DPDS) surfactants (C12 and C16 alkyl
moieties) with naphthalene in aqueous systems and phenanthrene in soil systems to investigate the
influence of these surfactants on biodegradation of hydrocarbons. A potential for enhancement in the
degradation of naphthalene was seen in C12-DPDS amended assays at low surfactant concentrations,
predominately below the critical micelle concentration (CMC). The overall trend for both C12- and
C16-DPDS assays indicated decreasing efficiency in degradation of naphthalene with increasing surfactant
concentration, with no correlation to the CMCs. In the soil-slurry assays, surfactant-free controls
and assays with the lowest (sub-CMC) surfactant additions demonstrated the first phenanthrene
mineralization responses followed by the mid-level (sub-CMC) surfactant-amended assays.
Approximately 3 months later, a supra-CMC C12-DPDS sample had a strong response. In saturated
soil (mud) systems, mineralization only occurred in the surfactant-free controls and in assays with the
lowest (sub-CMC) additions during 5 months of testing. The lowest surfactant additions, however, were
effective in enhancing mineralization of phenanthrene, with the first-order constant for the C12-DPDS
amended assays being increased by a factor of 5 over that of the surfactant-free controls.