A comprehensive review of the screening methodology for anaerobic biodegradability of surfactants

A biodegradability assay should mimic in situ conditions as closely as possible. If this is not entirely possible, the assayshould at least include inoculum from the site. This review attemptsto condense current literature on anaerobic biodegradability assayand propose a clear assessment methodology to determine the fatesurfactants in anaerobic environments. It has been well documentedthat surfactant concentrations toxic to the microflora can lead tounwarranted failure of biodegradability assays. Thus, an important recommendation is to first perform a toxicity evaluation with relevant controls. Based on the results of this evaluation, a Tier 1biodegradability assay that assesses the rate of formation of reducedendproducts or the consumption of a particular terminal electron acceptor is recommended and supported by current literature. Balancedchemical equations for the complete mineralization of the substrateare then used to compare the amount of transformation that actuallyoccurred with that theoretically expected. When required, resultsshould be confirmed by Tier 2 testing, which includes monitoring ofsubstrate disappearance over time using a variety of analytical tools.These recommended procedures are scientifically defensible and havethe potential of providing environmentally relevant information on thefate of surfactant materials in the environment.