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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Fresh water: Readily biodegradable (2 studies), inherently biodegradable (1 study)
Salt water: readily biodegradable (1 study)
Anaerobic conditions: degradable, complete mineralisation (1 study)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The biodegradation of ethanol was assessed at a number of concentrations using a non-adapted domestic sewage innoculum in a freshwater medium using a 20 day study. Rapid degradation was observed. In a study that used a method based on a proposed improvement to a Sturm guideline study to make it more suitable for volatile substances, ethanol was shown to be readily biodegradable. In both cases, degradation well in excess of 60% was seen with 5 days. Based on the results of these studies, ethanol meets the criteria to be classified as readily biodegradable.

The biodegradation of ethanol was assessed at a number of concentrations using an innoculum prepared from natural salt water and boosted with non-adapted domestic sewage innoculum in an artificial salt water medium. Degradation was observed to a level of 75% over 20 days and 68% in 10 days. This results shows it meets the requirement for designation as readily biodegradable in sea water.

In a study to assess the biodegradability of ethanol under anaerobic conditions, ethanol was exposed to methanogenic bacteria derived from an aquifer slurry. Degradation was followed by measuring the pressure increase through emissions of CH4 and CO2 and, at the end of the study, by GC analysis to quantify the amount of methane produced. After a lag time of 25 -30 days, methane emissions equivalent to 91% mineralisation was eventually seen (after an unquantified time) indicating biodegradability under anaerobic conditions.

The biodegradation data suggests a half life of around 3 days in water, which compares to other an estimated river half life of 6.5 -26 hours and a half life for aerobic degradation of 26 -104 hours.