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Environmental fate & pathways

Biodegradation in water: screening tests

Administrative data

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
December 2002 - April 2003
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to GLP and a OECD guidelines. As such, it is considered to be Klimisch 1.

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2003
Report Date:
2003

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
impurity
Test material form:
liquid
Specific details on test material used for the study:
Commercial name: Linalyl Isobutyrate
Chemical name: 3,7-dimethyl-1,6-octadien-3-yl 2-methylpropanoate
Empirical formula: C14H24O2
Molecular weight: 224.3 g/mol
CAS no: 78-35-3

Study design

Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City of Geneva, Peney-Dessous) was used. The sludge was collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g 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):
35 d
Initial test substance concentration
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test substance samples (25 mg, corresponding to 100 mg/I in a 250-ml flask) were weighed in small aluminium boats and added directly to the test flasks of the SAPROMAT. Reference substance samples (sodium benzoate) were added as 1.0 ml of a 25 mg/ml solution in mineral medium.All flasks were filled with 250 ml of mineral medium. Samples of test or reference substance, or both, were added. Then, a volume of suspended sludge corresponding to 7.5 mg dry weight (as determined from 3.6, generally 1 to 3 ml) was added.
About 2 g of soda lime was placed in an attachment of the stopper, the flasks were closed and placed in the water bath of the SAPROMAT. After temperature and pressure equilibration, the oxygen-meters of the instrument were set to zero (time zero of the experiment).
In order to check the toxicity of the test substance to the inoculum a pair of flasks of the volumetric respirometer were filled with mineral medium and the test substance (100 mg/L), plus the reference substance (100 mg/L) and inoculum. Their respiration rate was recorded as for the other flasks.
Reference substance
Reference substance:
benzoic acid, sodium salt

Results and discussion

Preliminary study:
Not applicable
Test performance:
Oxygen uptakes, as read on the SAPROMAT meters, were corrected to account for themsmall differences between actual and nominal concentrations of test and reference substances.
Degradation of sodium benzoate exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified.
% Degradationopen allclose all
Key result
Parameter:
% degradation (O2 consumption)
Value:
75
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
77
Sampling time:
35 d
Details on results:
The curves obtained with the reference substance alone and with Linalyl Isobutyrate + reference substance show no toxic effect of Linalyl Isobutyrate to the micro-organisms at the test concentration (100 mg/l).
Linalyl Isobutyrate undergoes 75% biodegradation after 28 days (77% after 35 days) in the test conditions. Biodegradation starts on say 4 and reaches 53% at the end of the 10-day window (days 4 to 14). Hence, the 10-day window is not fulfilled. The 10-day time window criterion was developed on the assumption that a test substance is degraded according to a 'standard' growth curve in ready biodegradability tests. However, esters are usually not viewed as a single substance by micro-organisms. Both hydrolysis products are sequentially degraded, often by different micro-organisms. The degradation curve will therefore not be a standard degradation curve, but the sum of different growth curves. The OECD Guidelinesfor Testing of Chemicals, Section . Part 1: Principles and strategies related to the testing and degradation of organic chemicals (adopted 23 March 2006), states that if 'it is anticipated that a sequential biodegradation of individual structures is taking place, then the 10-day window should not be applied to interpret the results of the test.' The 10-day window should therefore not be used as a pass / fail criterion. Thus, Linalyl Isobutyrate should be regarded as readily biodegradable according to this test based on the biodegradation percentage of 75% at day 28.

BOD5 / COD results

Results with reference substance:
Degradation of sodium benzoate exceeds 40 % after 7 days and 65 % after 14 days: the activity of the inoculum is thus verified.

Any other information on results incl. tables

Table 1: Measured concentrations of test substance.

Flask no.

Concentration of test substance (mg/L)

Concentration of reference substance (mg/L)

pH initial

pH final

1/5

0

100.2

7.54

8.07

1/6

0

100.2

7.54

8.07

1/7

0

0

7.54

7.63

1/8

0

0

7.54

7.64

2/1

102.6

100.2

7.54

8.23

2/2

104.4

100.2

7.54

8.25

2/3

104.9

0

7.54

7.63

2/4

106.3

0

7.54

7.64

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The curves obtained with the reference substance alone and with Linalyl Isobutyrate + reference substance show no toxic effect of Linalyl Isobutyrate to the micro-organisms at the test concentration (100 mg/l).
Linalyl Isobutyrate undergoes 75% biodegradation after 28 days (77% after 35 days) in the test conditions. Biodegradation starts on say 4 and reaches 53% at the end of the 10-day window (days 4 to 14). Hence, the 10-day window is not fulfilled. The 10-day time window criterion was developed on the assumption that a test substance is degraded according to a 'standard' growth curve in ready biodegradability tests. However, esters are usually not viewed as a single substance by micro-organisms. Both hydrolysis products are sequentially degraded, often by different micro-organisms. The degradation curve will therefore not be a standard degradation curve, but the sum of different growth curves. The OECD Guidelinesfor Testing of Chemicals, Section . Part 1: Principles and strategies related to the testing and degradation of organic chemicals (adopted 23 March 2006), states that if 'it is anticipated that a sequential biodegradation of individual structures is taking place, then the 10-day window should not be applied to interpret the results of the test.' The 10-day window should therefore not be used as a pass / fail criterion. Thus, Linalyl Isobutyrate should be regarded as readily biodegradable according to this test based on the biodegradation percentage of 75% at day 28.