Anaerobic biodegradability testing of surfactants

• Published in: Chemosphere (Oxford) 1995-03, Vol.30 (5), p.813-830
• Main Authors: Salanitro, Joseph P., Diaz, Luis A.
• Format: Article
• Language: English
• Subjects: anaerobic; anionic; Applied sciences; Bacteria, Anaerobic - metabolism; biodegradation; Biodegradation, Environmental; digesters; Exact sciences and technology; General purification processes; Methane - metabolism; nonionic; Pollution; pressure transducer assay; Sewage; Surface-Active Agents - chemistry; Surface-Active Agents - metabolism; surfactants; Transducers, Pressure - standards; Waste Disposal, Fluid; Wastewaters; Water treatment and pollution
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/0045-6535(94)00443-X

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 (A 45S and A 24S) 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.