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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012-10-04 to 2012-12-18
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Qualifier:
according to guideline
Guideline:
EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (Bois de Bay, Satigny, Switzerland) was used.
- Preparation of inoculum for exposure: The sludge is collected in the morning, washed three times in mineral medium (by centrifuging at 1000g for 10 minutes, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
Duration of test (contact time):
28 d
Initial conc.:
20 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium according to guideline
- Additional substrate: no
- Solubilising agent: no
- Test temperature: 21.4°C-22.3°C
- pH of medium: 7.4 ± 0.2
- pH of medium adjusted: yes, with phosphoric acid or potassium hydroxide
- Suspended solids concentration: 1.53 g dw/L

TEST SYSTEM
- Number of culture flasks/concentration: 6
2 flasks with inoculum and test substance; conc. of test substance: 20 mg/l;
2 flasks with only inoculum;
2 flasks with inoculum and reference substance; conc. of reference substance: 99 mg/l;

SAMPLING
- Sampling frequency: daily
- Reported values: on days 1, 2, 3, 12, 21, 28 and 35
- Sampling method: every day, the oxygen consumption of each flask is recorded and correct temperature and stirring checked. At the end of the test period, the pH of each flask is measured again.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 2 flasks
- Abiotic sterile control: no
- Toxicity control: no
Reference substance:
benzoic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
80
Sampling time:
28 d
Remarks on result:
other: More information on the results can be found at "Any other information on results incl. tables" field
Details on results:
Reference substance: degradation of the reference substance exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion). Moreover, the repeatability validity criterion (not more than 20% difference between replicates) is fulfilled for the flasks containing the test substance. Therefore, the test is considered valid.

Test item 10-day window: the criterion is fulfilled (15% biodegradation on day 2 and 75% on day 12).

Biodegradability: % biodegradation of test substance

replicate  days 
1 2 3 12 21 28 35
1 6 6 42 75 80 78 77
2 5 24 46 75 79 81 80
mean  5 15 44 75 79 80 79

Biodegradability: % biodegradation of reference substance

replicate  days 
5 7 14 21 28
1 72 77 85 89 88
2 78 81 95 98 97
mean  75 79 90 93 93
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test substance undergoes 80% biodegradation after 28 days in the test conditions. The 10-day window criterion is also fulfilled (15% biodegradation on day 2 and 75% on day 12).

The test substance should be regarded as readily biodegradable according to this test.
Executive summary:

The biodegradability of the test item was examined according to the manometric respirometry test method C.4 -D and according to OECD guideline 301F. After 28 days, the biodegradation was found to be 80%.

The 10 -day window criterion is also fulfilled: 15% biodegradation on day 2 and 75% on day 12. Hence, the test item should be considered to be readily biodegradable. Moreover, the test substance did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

The degradation of the reference substance exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion).

Description of key information

Readily biodegradable (80% biodegradation after 28 days; OECD 301 F)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

In a Manometric Respirometry Test (OECD 301 F) the test item undergoes 80% biodegradation after 28 days. In this GLP test, the 10 -day window criterion is also fulfilled: 15% biodegradation on day 2 and 75% on day 12. Hence, the test item should be considered to be readily biodegradable. Moreover, the test substance did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration.

The degradation of the reference substance exceeded 40% after 7 days and 65% after 14 days: the activity of the inoculum was thus verified (validity criterion).