2-ethylhexanoic acid, manganese salt

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Guideline study with acceptable restrictions (e.g. non-GLP; instead of secondary effluent as recommended by the guideline, the primary effluent of a municipal sewage treatment plant was used as inoculum for this study. The authors justified this by referring (1) to the microbial concentration in the secondary effluent that was too low for the purpose of the study, and (2) to the possible presence of chemical residues within the secondary effluent that may interfere with the biological activity.)

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic (adaptation not specified)

Details on inoculum:

INOCULUM :
- Target concentration of microbes in test solution (OECD 301 E): 10E+05 cells/L
- Origin of the inoculum : Municipal sewage treatment plant , Suomenoja , Espoo 26.05.1998
Concentration of inoculum : 1. Secondary effluent approx. 10E+03 - 10E+04 cells/ml; 2. Primary effluent approx. 10E+06 cells/ml
(Easycult TTC, Orion Diagnostica ); Inoculum 2. was used in the test to obtain sufficient microbe concentration
- Preparation of inoculum : Filtration (Schleicher & Schuell 5891 Black ribbon )
- Addition into test solution : 0.5 ml/I

Duration of test (contact time):

28 d

Initial conc.:

20 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS : Incubation shaker New Brunswick G25-KLC
Continuous shaking 120 rp m
Temperature 22 ± 2 °C
Dark
Test vessels 2 I conical flasks , volume of the test solution at start 1000 ml
Free exchange of air in test vessel s
SAMPLING: DOC-samples 50 ml/sampling time and flask
Filtration of samples with Gelman Ion chromatography Acrodisc 0 .45 pm
Storage of filtered samples in -20 °C before analysis

test series:
inoculum blank (inoculum + mineral medium),
test substance (inoculum + mineral medium + test substance),
reference substance (inoculum + mineral medium + reference substance),
toxicity test (inoculum + mineral medium + test substance + reference substance) - start conditions:

mineral medium: pH 7.6, 9 mg/l O2 (= 100 %),
test substance solution: pH 7.45

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (DOC removal)

Value:

99

Sampling time:

28 d

Parameter:

% degradation (DOC removal)

Value:

90.1

Sampling time:

7 d

Details on results:

RS-Freetext:
Biodegradation (% relate to DOC)

0 d 2 d 5 d 7 d 14 d 28 d
test substance
(mean) 0 67.2 91.4 90.7 94.9 99.2

reference
substance 0 83.8 97.8 95.6 96.8 99.3

toxicity test 0 76.1 98.2



Biodegradation 10 d window
10 % 70 %
test substance 0.3 d 2.3 d 0.3 d - 10.3 d

reference
substance 0.2 d 1.7 d 0.2 d - 10.2 d


Conclusion:
2-ethylhexanoic acid is readily biodegradable:
- biodegradation (28 d) > 70 %
- Pass level reached in 10-d window.

Kinetic of test substance (in %):
= 67 after 2 day(s)
= 91 after 5 day(s)
= 91 after 7 day(s)
= 95 after 14 day(s)
Kinetic of control substance (in %):
= 84 after 2 day(s)
= 98 after 5 day(s)
Degradation products: not measured

Abiotic and adsorption tests were poisoned with 15 mg/l Na azide to prevent bioactivity. The dosage was not sufficient to stop microbial  growth in test vessels, and so the tests were interrupted as the  preliminary results showed at the same time that these factors are not  likely to interfere the biodegradation of the test substance.

test has been performed by Ekolab Environmental Oy (sponsor: Finnish Chemicals Oy)

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Description of key information

2-ethylhexanoic acid is readily biodegradable (according to OECD criteria).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

As key study regarding biodegradability of 2-ethylhexanoic acid a test performed by Ekolab Environmental Oy on behalf of Finnish Chemical Oy (1998) was identified. The test was enforced according to OECD guideline 301E using primary effluent of municipal sewage treatment plant. After 28 days a DOC removal of 99% was measured.