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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:
October 2002 - January 2003.
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to a recognised guideline and is GLP compliant.

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
Test material form:
liquid
Details on test material:
Identification: Isobutyl phenyl acetate
Commercial name: Isobutyl phenyl acetate
Chemical nature: 2-methylpropyl phenylacetate
Empirical formula: C12H16O2
Molecular weight: 192.2 g/mol
CAS No.: 102-13-6
Appearance/physical state: Colorless liquid
Lot No: 9000466715
Purity: 99.9%
Expiry date: 14 April 2004

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 is 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
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/l in a 250-ml flask) were weighed in small aluminium boats and added directly to the test flasks of the SAPROMAT, whereas 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 is placed in an attachment of the stopper, the flasks are closed and placed in the water bath of the SAPROMAT. After temperature and pressure equilibration, the oxygen-meters of the instrument are set to zero (time zero of the experiment).
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 the small 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 (validity criterion).
% Degradationopen allclose all
Key result
Parameter:
% degradation (O2 consumption)
Value:
83
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
84
Sampling time:
35 d
Details on results:
Isobutyl Phenylacetate underwent 83% biodegradation after 28 days (84% after 35 days) in the test conditions. Biodegradation starts on day 2 and reaches 78% at the end of the 10-day window (days 2 to 12).
The curves obtained with the reference substance alone and with Isobutyl Phenylacetate + reference substance show no toxic effect of Isobutyl Phenylacetate to the micro-organisms at the test concentration (100 mg/l).
Thus, Isobutyl Phenylacetate should be regarded as readily biodegradable according to this test.

BOD5 / COD results

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

Any other information on results incl. tables

Table 1: Measured concentrations and pH values for test and reference substances

Flask no.

Concentrations (mg/L

pH

Test subst.

Ref. Subst.

Initial

Final

1/9

0

0

7.44

7.52

1/10

0

0

7.44

7.39

1/11

0

100.1

7.44

7.74

1/12

0

100.1

7.44

7.92

2/9

103.0

100.1

7.44

7.99

2/10

104.4

100.1

7.44

7.99

2/11

105.2

0

7.44

7.49

2/12

105.7

0

7.44

7.45

Table 2: Biological oxygen demand (BOD) and % degradation

 

Days

2

7

12

21

28

35

BOD Sludge

1stflask

9.0

20.0

25.0

29.0

31.0

33.0

2ndflask

8.0

20.0

26.0

34.0

40.0

48.0

mean

8.5

20.0

25.5

31.5

35.5

40.5

BOD Test Subs.

1stflask

81.2

206.3

227.5

244.0

248.0

253.9

2ndflask

78.0

193.2

213.3

231.6

239.4

246.3

1stflask corrected

72.7

186.3

202.0

212.5

212.5

213.4

2ndflask corrected

69.5

173.2

187.8

200.1

203.9

205.8

% degr.

1stflask

29

75

81

85

85

85

2ndflask

28

69

75

80

82

82

mean

28

72

78

83

83

84

Applicant's summary and conclusion

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Isobutyl Phenylacetate was 83% biodegraded after 28 days, and the 10-day window was met. Therefore, Isobutyl Phenylacetate is regarded as readily biodegradable according to this study.
Executive summary:

The ready biodegradability of Isobutyl Phenylacetate was determined by the Manometric Respirometry Test according to the OECD Guidelines for Testing of Chemicals, Method No. 301 F. Isobutyl Phenylacetate undergoes 83% biodegradation after 28 days (84% after 35 days) in the test conditions. Biodegradation starts on day 2 and reaches 78% at the end of the 10-day window (days 2 to 12). The curves obtained with the reference substance alone and with Isobutyl Phenylacetate + reference substance show no toxic effect of Isobutyl Phenylacetate to the micro-organisms at the test concentration (100 mg/l). Thus, Isobutyl Phenylacetate should be regarded as readily biodegradable according to this test.