Registration Dossier

Diss Factsheets

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

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

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
1992
Report date:
1992

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to guideline
Guideline:
other: Official Journal of the European Communities, 84/449/EEC, L251, 27, 19 September 1984, Method C.6. Degradation, Biotic Degradation: Closed Bottle Test.
Deviations:
no
GLP compliance:
yes

Test material

Constituent 1
Chemical structure
Reference substance name:
4-Ethenylphenyl acetate
Cas Number:
2628-16-2
Molecular formula:
C10H10O2
IUPAC Name:
4-Ethenylphenyl acetate
Test material form:
liquid
Details on test material:
- Purity: not reported

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
sewage, domestic (adaptation not specified)
Details on inoculum:
Secondary effluent collected on the day of test from a trickling-filter plant at a sewage treatment works that predominatly treats domestic waste. Maintained under aerobic conditions in laboratory, then, immediately before use, vacuum-filtered through a Whatman's GFC filter paper and the filtrate used as the inoculum for the test (1 drop filtrate/litre test medium).
Duration of test (contact time):
28 d
Initial test substance concentration
Initial conc.:
2 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The medium is prepared by adding 1 mL of each stock soltuion to each litre of purified water.
Stock Solution 1: Potassium dihydrogen phosphate (8.5 g/L), di potassium hydrogen phosphate (21.75 g/L), di sodium monohydrogen phosphate dihydrate (33.30 g/L), ammonium chloride (1.70 g/L)
Stock Solution 2: Magnesium sulphate heptahydrate (22.50 g/L)
Stock Solution 3: Calcium chloride dihydrate (36.40 g/L)
Stock Solution 4: Iron (III) chloride hexahydrate (0.25 g/L)
- Additional substrate: Sodium Benzoate was used as a reference
- Incubation temperature: 20°C
- pH adjusted: no

TEST SYSTEM
- Number of culture flasks/concentration:
Medium alone: 8 flasks
Medium + inoculum: 8 flasks
Medium + inoculum + sodium benzoate (2 mg/L): 8 flasks
Medium + inoculum + test substance (2 mg/L): 12 flasks
- Measuring equipment: oxygen concentrations were measured using a YSI dissolved oxygen meter fitted with a self-stirring DO/temperature bottle probe.


SAMPLING
- Sampling frequency: Days 0, 5, 15, and 28
- Sampling method: DO/temperature probe; pH was taken after oxygen and temperature measurement
-Concentration of disolved oxygen was measured in duplicate on Day 0 from each group of flasks
- Sampling of test substance: 2 flasks on Day 5, 4 flasks on Day 15, and 4 flasks on day 28
Reference substance
Reference substance:
benzoic acid, sodium salt
Remarks:
2 mg/L

Results and discussion

Test performance:
Test was run twice. In the initial test conducted, the test substance degraded 7%, 53%, and 22% of ThODon Days 5, 15, and 28 respectively. The oxygen consumption on Day 28 was considered to be unacceptably low compared to Day 15 so the test was repeated to obtain a more reliable estimate of degradation. The results obtained only in the second test were fully reported.
% Degradationopen allclose all
Key result
Parameter:
% degradation (O2 consumption)
Value:
11
Sampling time:
5 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
57
Sampling time:
15 d
Remarks on result:
other: range of 55-62%
Key result
Parameter:
% degradation (O2 consumption)
Value:
48
Sampling time:
28 d
Remarks on result:
other: range of 46-53%
Details on results:
- Test temperature: Day 0: 20.1 - 20.3°C, Day 5: 19.6 - 20.1°C, Day 15: 19.5 - 19.7°C, Day 28: 18.8 - 19.0°C
- pH: Day 0: 7.19 - 7.29, Day 5: 7.26 - 7.40, Day 15: 7.17 - 7.50, Day 28: 6.58 - 7.23

ThOD was calculated to be 2.27 mgO2/mg for the test substance. The percentage of degradation calculated at each sampling point is based on the ThOD value. The mean oxygen consumption of the test substance was equivalent to 11%, 57%, and 48% of it's ThOD on Days 5, 15, and 28 respectively.

The slightly lower levels of degradation observed on Day 28 of the test are not unusual and are not thought to have affected the final result.

Oxygen consumption by Day 28 in control bottles containing uninoculated and inoculated medium were 0.2 and 0.1 mgO2/L, were within the acceptable range for this assay system (less than 0.4 and 0.6 mgO2/L respectively)

BOD5 / COD results

BOD5 / CODopen allclose all
Key result
Parameter:
BOD5
Value:
0.25 other: mgO2/mg test material
Remarks on result:
other: Day 5
Remarks:
mean of 2 flasks
Key result
Parameter:
BOD5
Value:
1.3 other: mgO2/mg test material
Remarks on result:
other: Day 15
Remarks:
mean of 4 flasks
Key result
Parameter:
BOD5
Value:
1.1 other: mgO2/mg test material
Remarks on result:
other: Day 28
Remarks:
mean of 4 flasks
Results with reference substance:
Sodium benzoate was degraded to 59% of its ThOD (1.67 mgO2/mg) after 5 days of incubation and 66% and 45% on Days 15 and 28 respectively. Degradation achieved the 10% level after approximately 1 day of incubation and the 60% level after approximately eight days. This confirms that the inoculum was viable and exerting normal biodegradation activity and the test was valid. The slightly lower levels of degradation observed on Day 28 of the test are not unusual and are not thought to have affected the final result.

Any other information on results incl. tables

Table 1: Mean oxygen consumption
Mean oxygen concentration (mgO2/L) Oxygen Consumption (mgO2/L)
Group Day 0 Day 5 Day 15 Day 28 Day 5 Day 15 Day 28
Medium only 9.1 8.9 9.0 8.9 0.2 0.1 0.2
Medium + inoculum 9.0 8.9 8.9 9.0 0.2 0.2 0.1
Medium + inoculum + sodium benzoate 9.1 7.0 6.7 7.5 1.9 2.2 1.5
Medium + inoculum + test substance 9.1 8.4 6.3 6.8 0.5 2.6

2.2

Table 2: BOD (mgO2/mg) and percentage of degradation
BOD (mgO2/mg) Percentage degradation
Day 5 Day 15 Day 28 Day 5 Day 15 Day 28
Medium + inoculum + sodium benzoate 0.95 1.10 0.75 57% 66% 45%
  1.00 1.10 0.75 60% 66% 45%
Mean % degradation       59% 66% 45%
Medium + inoculum + test substance 0.25 1.25 1.05 11% 55% 46%
  0.25 1.25 1.05 11% 55% 46%
    1.25 1.05   55% 46%
    1.4 1.2   62% 53%
Mean % degradation       11% 57% 48%

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Mean degradation of the test substance by Day 15: 57% based on ThOD
Executive summary:

The objective of this study was to assess the biotic degradation of the test substance following OECD 301D and Procedure C.6 of EEC Directive 84/449/EEC.

An aqueous solution of the test substance was added to mineral salts medium and inoculated with sewage effluent to give a nominal concentration of 2 mg/L and the mixture was transferred to 12 BOD bottles. Control sets of bottles contained either salts medium only, inoculated salts medium, or inoculated salts medium and sodium benzoate (2 mg/L). The concentrations of dissolved oxygen in duplicate bottles was taken from each group at the start of the test (Day 0) and after 5, 15, and 28 days of incubation at 20°C, in darkness. Two bottles with the test substance were used for oxygen measurement on Day 5; four were taken on Days 15 and 28 to obtain more reliable estimate of degradation in the latter stages of the test.

The mean degradation of sodium benzoate was 59% of its ThOD (1.67 mg O2/mg) after 5 days of incubation and 66% and 45% on Days 15 and 28 respectively. These results confirm that the inoculum was exhibiting normal biodegradative activity and that the test was valid. The slightly lower level of degradation obtained for benzoate on Day 28 is not thought to be significant or to thave affected the validity of the final result.

Oxygen consumtion by Day 28 in control bottles containing uninoculated and inoculated medium was 0.2 and 0.1 mg O2/L and were considered within the normal range for this assay system (less than 0.4 and 0.6 mg O2/L respectively).

Mean oxygen consumption in bottles containing the test substance was equivalent to 11% of its ThOD on Day 5, 57% on Day 15, and 48% on Day 28.  Substances are considered readily degradable in this test if oxygen consumption is equal to or greater than 60% of the theoretical value in a ten-day period after the level of degradation exceees 10%.  Since degradation typically follows a sigmoidal curve whose precise form cannot be accurately defined in a Closed Bottle Test, it is considered that the extent to which the test substance degraded between Day 5 and Day 15, shows that it can be considered readily biodegradable.