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Biodegradation in water: screening tests

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Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes
Specific details on test material used for the study:
Clear colourless liquid, purity 96.5%.
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic (adaptation not specified)
Details on inoculum:
4 ml filtrate of secondary effluent from municipal sewage treatment plant (Waterschap de maaskant, ‘s-Hertogenbosch) per liter of final volume
Duration of test (contact time):
28 d
Initial conc.:
0.75 mg/L
Based on:
test mat.
Initial conc.:
3 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Temperature of incubation: 21.8-22.7 oC
Sampling frequency: In duplicate, after t=0, 7, 14, 21 and 28 days
Appropriate controls and blank system used: Yes, inoculum blank, procedure control, test suspension and toxicity control were used
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
0.75 mg/l sample
Value:
-6
Sampling time:
7 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
0.75 mg/l sample
Value:
4
Sampling time:
14 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
0.75 mg/l sample
Value:
8
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
0.75 mg/l sample
Value:
4
Sampling time:
28 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
3 mg/l sample
Value:
-2
Sampling time:
7 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
3 mg/l sample
Value:
2
Sampling time:
14 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
3 mg/l sample
Value:
3
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Remarks:
3 mg/l sample
Value:
6
Sampling time:
28 d
Details on results:
The ThOD was calculated to be 2.2 mg O2/mg. After 28 days the relative biodegradation calculated from the O2 measurements showed no significant degradation of Pentamethyl-trioxepane at both conc. and the tox. control showed no inhibition of microbial activity.
Validity criteria fulfilled:
yes
Remarks:
O2 depletion in inoculum blank < 1.5mg O2/l after 28d (0.43mg), residual conc of O2 in test bottles > 0.5mg/l at any time, all differences of duplicate values as O2/l were < 20%, the control substance was degraded by at least 60% within 14d (66% on day 7)
Interpretation of results:
not readily biodegradable
Conclusions:
Pentamethyl-trioxepane was not readily biodegradable under the conditions of the closed bottle test presently performed.
Executive summary:

Pentamethyl-trioxepane was not readily biodegradable under the conditions of the closed bottle test presently performed.

Endpoint:
biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))
Deviations:
no
GLP compliance:
no
Remarks:
ISO 17025:2005
Specific details on test material used for the study:
colorless liquid, 98.4 % purity, stored at room temperature in the dark
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge (adaptation not specified)
Details on inoculum:
Sludge sampling is made, in principle, at not less than 10 places throughout the country, chiefly in those areas where a variety of chemical substances may be considered to be consumed and discarded.

The sludge samples collected from the sampling sites are mixed with the same volume by stirring in a single container, and the mixture is allowed to stand. Floating foreign matter is removed and the supernatant is filtered through No. 2 filter paper. The filtrate is adjusted to pH 7.0 +/- 1.0 with sodium hydroxide or phosphoric acid, transferred into a culture tank and aerated for 23.5h. About 30 minutes after ceasing the aeration of the solution obatined above approximately 1/3 of the whole volume of the supernatant is removed. An equal volume of 0.1 percent synthetic sewage (1 g of glucose, 1 g of peptones and 1 g of monopotassium phosphate are dissolved in 1 litre of water and the solution is adjusted to pH 7.0 +/- 1.0 with sodium hydroxide) is added to the remaining portion of the supernatant, and the mixture is aerated again. This procedure is repeated once every day. The culturing is carried out at 25 +/- 1.0 oC for one month.
Duration of test (contact time):
28 d
Initial conc.:
30 mg/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Preparation of bottles:

Bottle 1: deionised water, 1000 ml + test chemical, 30 mg
Bottles 2,3,4: basal culture medium, 1000 ml + activated sludge, 100 mg (dry basis) + test chemical 30 mg
Bottle 5: basal culture medium, 1000 ml + activated sludge, 100 mg (dry basis) + sodium lauryl sulfate, 100 mg
Bottle 6: basal culture medium, 1000 ml + activated sludge, 100 mg (dry basis)

Test validity:
Difference between parallel groups should be less than 20 %.
Degradation of the reference substance should exceed 40 % after 7 days and 65 % after 14 days.
Reference substance:
other: sodium lauryl sulfate (A.R.)
Test performance:
The viability of the inoculum and validity of the test were supported by the results of the reference substance, sodium lauryl sulfate.
Key result
Parameter:
% degradation (O2 consumption)
Value:
12.5
Sampling time:
7 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
17.3
Sampling time:
14 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
18.6
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
20.7
Sampling time:
28 d
Details on results:
The temperature range recorded during the test was 25 +/- 1.0 oC and was within the protocol specified range throughout the test.

The average oxygen uptake exhibited by the control, reference, and treatment groups at each sampling interval are as summarized herein.
Results with reference substance:
69.1 % @ 7 d, 79.9 % @ 14 d, 84.2 % @ 21 d, 86.1 % @ 28 d
Validity criteria fulfilled:
yes
Interpretation of results:
not inherently biodegradable
Conclusions:
As a result, the average percent biodegradation of the test substance 3,3,5,7,7-pentamethyl-1,2,4-trioxepane on days 7, 14, 21 and 28 was calculated as 12.5%, 17.3%, 18.6% and 20.7% under these test conditions.
Executive summary:

As a result, the average percent biodegradation of the test substance 3,3,5,7,7-pentamethyl-1,2,4-trioxepane on days 7, 14, 21 and 28 was calculated as 12.5%, 17.3%, 18.6% and 20.7% under these test conditions.

Description of key information

Pentamethyl-trioxepane was not readily biodegradable in the closed bottle test and achieved only 20.7 % degradation after 28 days in OECD 302C (MITI II)

Key value for chemical safety assessment

Additional information