Phenol, heptyl derivs.

Biodegradation in water: screening tests

Description of key information

The substance is not readily biodegradable. A supplementary study shows the substance is inherently biodegradable in the presence of preadapted sewage sludge micro-organisms

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, fulfilling specific criteria

Additional information

In the key study performed according to OECD 301D Closed Bottle Test Method inoculated test medium is dosed with a known amount of test substance as the nominal sole source of organic carbon. Degradation is followed by the analysis of dissolved oxygen over a 28-day test period. The dissolved oxygen uptake of the test solution (corrected for uptake of blank inoculum) is expressed as a percentage of the theoretical oxygen demand (ThOD) for the reference substance and chemical oxygen demand (COD) for the test substance. The test contained an inoculum control group, a reference group, treatment group, and a toxicity control group. The control, reference and treatment groups each contained twenty replicate test chambers. The toxicity control group contained four replicate test chambers. The inoculum control was used to measure the oxygen uptake of the inoculum and was not dosed with a carbon source. The reference chambers were dosed with sodium benzoate, a substance known to be biodegradable, at a nominal concentration of 2 mg/L. The treatment group test chambers were used to evaluate the test substance at a nominal concentration of 5 mg/L. The toxicity control group test chambers were used to evaluate toxicity of the test substance on the inoculum dosed at nominal concentrations of 2 mg/L (reference) and 5 mg/L (test substance). Measurements of dissolved oxygen were performed on two test chambers from the control, reference and treatment groups once a week and the toxicity control group on Days 0 and 14.

The results indicate that the inoculum was active by degrading the reference substance within the acceptable range. The results for the test substance were an average of 1.6% degradation over a 28-day test period.

The test substance is not readily biodegradable under the conditions of the study.

In a supplementary study determination of biodegradation was performed according to OECD 301B, US EPA 796.3260 and ASTM D 5864 -95.

The test material, at a concentration of 10 mg carbon/L was exposed to a preadapted mixed culture inoculum derived from activated sewage sludge/soil with culture medium at 20°C for 28 days (pH 7). CO2 released from the degradation chamber was trapped and the amounts measured at the sample periods. Results are expressed as a percentage of the theoretical total amount of CO2 that could be produced by complete degradation.

The test material reached 25.4% biodegradation after 28 days.

The test material undergoes degradation with preadaptation of inoculum under the conditions of the study. As the substance does not reach 60% degradation after 28 days it cannot be considered to be readily biodegradable, but shows the substance is inherently biodegradable.