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Biodegradation in water: screening tests

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biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: This summary represents a key study because it followed an OECD standard guideline, which describes a procedure specifically designed to evaluate this endpoint, and the results were reviewed for reliability and assessed as valid.
according to guideline
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Version / remarks:
GLP compliance:
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Inoculum used as the source of the microorganisms was an aliquot of fresh activated sludge from a domestic wastewater treatment facility in New Jersey, USA.
Duration of test (contact time):
28 d
Initial conc.:
45 mg/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test material was tested in triplicate, controls and blanks were tested in duplicate. The amount of oxygen consumed by microorganisms from the oxidation of the test material was continuously monitored by an automated respirometer during the 28-day test period. Test material concentration was 45mg/L. Sodium benzoate (positive control) concentration was 50mg/L. All test vessels were stirred constantly for 28 days using magnetic stir bars and plates.
Reference substance:
benzoic acid, sodium salt
% degradation (O2 consumption)
Sampling time:
2 d
% degradation (O2 consumption)
Sampling time:
7 d
% degradation (O2 consumption)
Sampling time:
10 d
Key result
% degradation (O2 consumption)
Sampling time:
28 d
Details on results:
% Degradation on day 28: 79.5, 78.6, 76.0
Results with reference substance:
% Degradation on day 28: 88.7, 88.9
Mean % Degradation: 88.8

The biodegradation half-life was <2 weeks. By day 28, 78.0% degradation of the test material was observed. 10% biodegradation was achieved on approximately day 3, 50% biodegradation on approximately day 7.

By day 14, >60% biodegradation of positive control was observed, which meets the guideline requirement. No deviations from the protocol were noted. Biodegradation was based on oxygen consumption and the theoretical oxygen demand of the test material as calculated using results of an elemental analysis of the test material.

Validity criteria fulfilled:
Interpretation of results:
readily biodegradable
Biodegradation was greater than 60% in 28 days, therefore the test substance is readily biodegradable.
Executive summary:

This study was done to determine the ready biodegradability of the test substance. 45 mg/l of test stubstance was added to test medium containing activated sludge. The O2 consumption of the sludge was then monitored for the next 28 days. The test substance was degraded 78% in 28 days. The reference substance, sodium benzoate, was degraded 88.8% in 28 days, so the test is considered valid. The test substance is therefore readily biodegradable.

Description of key information

There is data available for this substance. Key data is summarized below.

Hydrocarbons, C9, aromatics, were inherently to readily biodegradable in an OECD 301B, 301D and OECD 301F Manometric Respirometry test. The OECD 301F test resulted in 78% biodegradation in 28 days using a predominantly domestic aerobic non-acclimated activated sewage sludge inoculum. The OECD 301B and 301D tests resulted in 56% and 21%, respectively.

Key value for chemical safety assessment

Additional information