Hydrocarbons, C13-C15, n-alkanes, isoalkanes, cyclics, < 2% aromatics

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

August to September 1994

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was conducted according to a standard guideline without deviations from the protocol and was conducted under GLP guidelines.

Reason / purpose for cross-reference:

read-across: supporting information

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

An un-acclimated activated sludge inoculum was used in this study. The inoculum was obtained from the Somerset Raritan Valley Sewage Authority, Bridgewater, New Jersey, USA. The treatment plant receives predominantly domestic sewage. The sewage sample was obtained one day prior to test initiation. The microbial count was 106 CFU/mL. The sludge supernatant was added at a 1% loading volume of to test medium. Test medium consisted of glass distilled water and mineral salts (phosphate buffer, ferric chloride, magnesium sulfate, calcium chloride). One liter of test medium and activated sludge, which was aerated for 24 hours with carbon dioxide free air, was added to each one liter respirometer flask.

Duration of test (contact time):

28 d

Initial conc.:

ca. 38 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Triplicate test systems were used to evaluate the biodegradability of the test substance and the positive control substance at mean concentrations of approximately 38 mg/L and 50 mg/L, respectively. Blank test systems, which did not contain the test or positive control substance, were run concurrently in triplicate. The test substance was weighed in an air tight syringe and injected into the test medium. The test system was sealed immediately after addition of the test substance. An aliquot of the positive control stock solution was added to the appropriate test flasks. All test vessels were stirred constantly using magnetic stir bars and plates. The study was conducted at a temperature of 21°C.

Reference substance:

benzoic acid, sodium salt

Preliminary study:

A preliminary study was not conducted.

Test performance:

No deviations from the protocol occurred that affected the integrity of the study data.

Parameter:

% degradation (O2 consumption)

Value:

4.8

Sampling time:

2 d

Parameter:

% degradation (O2 consumption)

Value:

12.7

Sampling time:

3 d

Parameter:

% degradation (O2 consumption)

Value:

53

Sampling time:

12 d

Parameter:

% degradation (O2 consumption)

Value:

60.2

Sampling time:

18 d

Parameter:

% degradation (O2 consumption)

Value:

67.6

Sampling time:

28 d

Remarks on result:

other: Percent biodegradation was still increasing.

Details on results:

The test substance exhibited rapid biodegradation, and assessed as readily biodegradable. The half-life was approximately 12 days. By Day 31, the average percent biodegradation of the test substance was 68.7%. The test substance reached 10% biodegradation on approximately Day 3 and 60% biodegradation on approximately Day 18.

Biodegradation was based on oxygen consumption and the theoretical oxygen demand of the test substance was calculated using results of an elemental analysis of the test substance.

Results with reference substance:

The reference substance biodegraded to an extent of 88.7% after 28 days. By Day 3, >60% biodegradation of the positive control was observed, which meets the guideline requirement.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable, but failing 10-day window

Conclusions:

The test substance, a multi-component substance, biodegraded to an extent of 68% after 28 days and 69% after 31 days. The data support characterizing the test substance as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10-day window requirement, it is characterized as readily biodegradable because the criterium is not applied to multi-component substances when assessing their ready biodegradability.

Executive summary:

The test substance, a multi-component substance, biodegraded to an extent of 68% after 28 days and 69% after 31 days. The data support characterizing the test substance as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10-day window requirement, it is characterized as readily biodegradable because the criterium is not applied to multi-component substances when assessing their ready biodegradability.

Description of key information

Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics, a multi-component substance, biodegraded to an extent of 69% after 28 days. The data support characterizing Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10-day window requirement, it is characterized as readily biodegradable because the criterium is not applied to multi-component substances when assessing their ready biodegradability.

Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, <2% aromatics, a multi-component substance, biodegraded to an extent of 68% after 28 days and 69% after 31 days. The data support characterizing Hydrocarbons, C12-C16, n-alkanes, isoalkanes, cyclics, <2% aromatics as rapidly biodegradable, readily biodegradable, not expected to persist in the environment under aerobic conditions. Although it did not meet the 10-day window requirement, it is characterized as readily biodegradable because the criterium is not applied to multi-component substances when assessing their ready biodegradability.