Distillation residue, butyl alcohols production, rectification

Biodegradation in water: screening tests

Description of key information

The study was carried out according to OECD guideline number 301B, and was conducted in compliance with the Principles of Good Laboratory Practice. A  known concentration of the test substance and domestic activated sludge inoculum was aerated by CO2-free air at controlled flow rate in diffuse light conditions.  Degradation was followed over 28 days determining the CO2 production in each test flask. Because the test substance is an UVCB- substance with unknown and variable composition, theoretical CO2 evolution was calculated based on the test substance concentrations (mass added into the test vessels) corresponding the TOC analysed from the test substance before initial biodegradation study. The biodegradation of the test substance was calculated and the overall degradation of the substance was evaluated from the graphical presentation in which the calculated biodegradation -% was plotted against time (days). 

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable

Additional information

The substance is a UVCB-substance which is a by-product of butyl alcohol production by propylene oxosynthesis manufactured at petrochemical industry. According to the test results, the substance is inherently biodegradable. The biodegradation of the test substance within 28 days was 49.6 %. Test substance did not attain 60 % of degradation within 10 days. Test substance was biodegradable but failing the 10 days-window. There might be some uncertainties related to the biodegradation results. The differences in physico-chemical properties of the constituents in the substance (i.e. solubility, vapour pressure) might have an influence on the overall biodegradation of the mixture. The modified strum test (OECD 301B) was conducted for this substance because this test method is most commonly used for petroleum substances which are comparable with the test substance. This study is performed in open system where aeration was used. This prodecure might have an effect on maintaining substance concentration during testing. Aeration might have increased the volatilisation of some constituents resulting partial loss of some constituents from test media. This phenomenon was studied by determining the stability of the substance. In this stability test, TOC concentration of the mixture was decreased by 18 % compared to the initial TOC conc. of the mixture during 1.5 hours aeration. According to the recommendations of the test laboratory, it might be more appropriate to use a closed system in order to avoid partial evaporation during testing. However, other technical problems will then arise related to the analytical uncertainties, e.g. calculation of ThOD, which will be very complicated for this substance of unknown and variable composition. As a conclusion, the interpretation of the biodegradation of this substance is inherently biodegradable because this substance is a hydrocarbon UVCB similar to petroleum products.