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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1 April - 13 May 1998
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
Negative biodegradation levels were observed during the first 30 days of the test which could be indicative of toxicity of the test substance to the inoculum.
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Material Identification (as stated in the report) : Gyrane
Appearance: Colourless to pale yellow liquid
Batch: 267261
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Fresh activated sludge collected from a biological waste treatment plant treating predominantly domestic sewage (City of Geneva, Aïre, Switzerland)
- Preparation of inoculum for exposure: Sludge was collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 min, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
- Concentration of sludge (suspended solids): 6.426 g/L (dry weight)
Duration of test (contact time):
41 d
Initial conc.:
30 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
other: Sodium Benzoate
Key result
Parameter:
% degradation (O2 consumption)
Value:
21
Sampling time:
41 d
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Details on results:
GYRANE undergoes no biodegradation after 28 days in the test conditions. A partial biodegradation starts on day 30 and reaches 21% after 41 days. Negative biodegradation levels were observed during the first 30 days which could be interpreted in terms of toxicity of the substance to the inoculum. A previous test (97-E104) showed that at higher concentration (100 mg/L) GYRANE was not inhibitory to the activated sludge micro-organisms. However, in the previous test the toxicity was assessed, as suggested in the OECD 301F method, by comparing the respiration of a flask containing the test chemical and a readily biodegradable reference substance with the respiration of a flask containing only the readily biodegradable reference substance. Since the flask containing test substance + reference item did not have a lower respiration than the flask containing only the reference item, it was concluded that the test chemical was not inhibitory. However, a toxicity test which is based on the effect of a test substance on the degradation of a readily biodegradable reference item may be less sensitive than assessing the intrinsic respiration of the inoculum to the test substance alone. Two key issues in using the former method to evaluate the toxicity of a substance to be assessed for biodegradability are described by Reynolds et al (1987). The first is that for easily degradable substrates the initial number of active micro-organisms in the inoculum will not be critical. Even if a large proportion of the inoculum is killed, the remaining organisms will proliferate and degrade the substance, still giving a high degradadation rate with no indication of the toxic effect of the test substance added. The second is that effect of the test substance on the degradation of a reference substance may not reflect the effects of the test substance on those microorganism species responsible for degrading it.

LITERATURE REFERENCE:
Reynolds L., Blok J., de Morsier A., Gerike P., Wellens H., Bontinck, W.J. (1987). Evaluation of the toxicity of substances to be assessed for biodegradability. Chemosphere, 16, 2259.
Results with reference substance:
- Sodium benzoate (ThOD is 1.67 mg O2/mg): 82% and 88% biodegradation after 7 and 14 days, respectively was achieved (meeting validity criterium).
Validity criteria fulfilled:
yes
Interpretation of results:
other: partially degraded
Conclusions:
GYRANE showed no biodegradation after 28 days but 21% after 41 days in the test conditions.Biodegradation above 20% may be regarded as evidence of inherent, primary biodegradation, whereas biodegradation above 70% may be regarded as evidence of inherent, ultimate biodegradability.Thus, GYRANE should be regarded as not inherently and ultimately biodegradable but as partially biodegradable, according to this test.
Executive summary:

The inherent biodegradability of GYRANE was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method 302C.

GYRANE undergoes no biodegradation after 28 days in the test conditions. A partial biodegradation starts on day 30 but reaches only 21% after 41 days.

Thus, GYRANE should be regarded as not inherently but only partially biodegradable after a long adaptation time, according to this test.

The inherent biodegradability of GYRANE was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method 302C.

When assessing inherent biodegradability it is not necessary to define limits on test duration. GYRANE showed no biodegradation after 28 days but 21% after 41 days in the test conditions.Biodegradation above 20% may be regarded as evidence of inherent, primary biodegradation, whereas biodegradation above 70% may be regarded as evidence of inherent, ultimate biodegradability.Thus, GYRANE should be regarded as not inherently and ultimately biodegradable but as partially biodegradable.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
10 October 1997 - 6 January 1998
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Material Identification (as stated in the report) : Gyrane
Appearance: Colourless to pale yellow liquid
Batch: 267261
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Fresh activated sludge collected from a biological waste treatment plant treating predominantly domestic sewage (City of Geneva. Aïre, Switzerland)
- Preparation of inoculum for exposure: Sludge was collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 min, discarding the supernatant and resuspending in mineral medium) and kept aerobic until being used on the same day.
- Concentration suspended solids in sludge: 2.28 g/L. This was diluted to 30 mg/L in the test vessels.
Duration of test (contact time):
28 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Reference substance:
other: Sodium benzoate
Key result
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Results with reference substance:
- Sodium benzoate (ThOD is 1.67 mg O2/mg): more than 40% biodegradation after 7 days (88%) and more than 65% degradation after 14 days (100%) was achieved.
Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Under the conditions of the Manometric respirometry test no biodegradation was observed. The test substance is not readily biodegradable.
Executive summary:

The ready biodegradability of GYRANE was determined by the Manometric Respiratory Test according to the OECD Guidelines for the testing of Chemicals, method 301F.

Gyrane undergoes no biodegradation after 28 days in the test conditions. Thus, Gyrane should be regarded as not readily biodegradable according to this test. At the concentration used in the test (100mg/L), GYRANE is not inhibitory to the micro-organism.

Description of key information

The ready biodegradability of GYRANE was determined by the Manometric Respiratory Test according to the OECD Guidelines for the testing of Chemicals, method 301F.

Gyrane undergoes no biodegradation after 28 days in the test conditions. Thus, Gyrane should be regarded as not readily biodegradable according to this test.

The inherent biodegradability of GYRANE was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method 302C.

When assessing inherent biodegradability it is not necessary to define limits on test duration. GYRANE showed no biodegradation after 28 days but 21% after 41 days in the test conditions. Biodegradation above 20% may be regarded as evidence of inherent, primary biodegradation, whereas biodegradation above 70% may be regarded as evidence of inherent, ultimate biodegradability. Thus, GYRANE should be regarded as not inherently and ultimately biodegradable but as partially biodegradable.

Key value for chemical safety assessment

Additional information