title: Anaerobic biodegradability testing of surfactants.
abstract: Anionic and nonionic surfactants (5-50 mg C/g solids/L medium) were screened for anaerobic microbial decomposition to methane in an automated pressure transducer serum bottle assay system at 35C using municipal digester solids as a source of anaerobic bacteria. Analysis of the headspace gas recovered from tests with linear primary alcohol sulfates (A45S and A24S) and a linear alcohol ethoxylate (LAE-8) showed that these compounds were readily degraded (60-85% of the theoretical methane, TM) after a 15-30 day lag period at 50 ppm C. The extent of degradation of a branched alkyl phenol ethoxylate (NPE-9) was lower (30-40% TM). A survey of intact nonionic and anionic surfactants present in municipal digester sludges in the U.S. showed that these materials were present at levels of 0.5-8 mg CTAS or MBAS/g dry solids. A surfactant which was slower to biodegrade (NPE-9) at 50 ppm C was readily metabolized to methane when tested at 5 and 10 mg C/g solids/L. The pressure transducer serum bottle method described may be used to test biodegradability and inhibitory effects on methanogenesis at surfactant concentrations (e.g. 5 ppm C/g solids) typically present in digesters.
authors.affiliation: Shell Development Company, Westhollow Technology Center, Houston, TX 77251-1380.
authors.forename: J P
authors.initials: JP
authors.lastname: Salanitro
authors.forename: L A
authors.initials: LA
authors.lastname: Diaz
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001673:Biodegradation, Environmental; D008697:Methane / Q000378:metabolism; D012722:Sewage; D013501:Surface-Active Agents / Q000737:chemistry / Q000378:metabolism*; D014160:Transducers, Pressure / Q000592:standards; D014865:Waste Disposal, Fluid
chemical_list: D012722:Sewage; D013501:Surface-Active Agents; D008697:Methane