Biodegradation of α-Olefin Sulfonates (AOS) and Other Surfactants

To follow the progress of biodegradation of anionic surfactants, the methylene blue method is the most widely employed for quantitative analysis. But, there is unaccountably the case in which the activity to methylene blue disappeared even before surfactant has not yet completely been biodegraded into inorganic compounds. And so, we examined the biodegradability of several surfactants by measuring the residual carbonaceous materials in comparison with the colorimetric analysis.Sodium α-olefin sulfonates (AOS) and other ten anionic and three nonionic surfactants were taken as test materials. In the shake culture test method, it was found that surfactants containing straight alkyl chain such as AOS, alcohol sulfate and soap were degraded in shorter period necessary for the disappearance of the carbonaceous materials during biodegradation. However, surfactants having benzene ring or ethoxylate chain in their molecules were slow in decrease of the concentration of organic carbon during biodegradation, and there was a large discrepancy between the biodegradation rates obtained by colorimetric analysis and measurement of organic carbon.