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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2012
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Well documented GLP study according to international guideline
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Version / remarks:
1992
Deviations:
yes
Remarks:
NH4Cl was omitted from the medium to prevent oxygen consumption due to nitrification
Qualifier:
according to guideline
Guideline:
other: ISO Test Guidelines 10107 (1994)
Qualifier:
according to guideline
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Version / remarks:
1992
GLP compliance:
yes (incl. QA statement)
Remarks:
Certifcate dates from 2010. The test substance data were submitted by the sponsor (unless stated otherwise), who accepted full responsibility for the validity of these data.
Oxygen conditions:
aerobic
Inoculum or test system:
natural water
Details on inoculum:
- Source of inoculum: River water was sampled from the Rhine near Heveadorp, the Netherlands (19-
01-2012). The nearest plant (Arnhem-Zuid) treating domestic wastewater
biologically was 3 km upstream.
- Preparation of inoculum for exposure: The river water was aerated for 7 days before
use to reduce the endogenous respiration. River
water without particles was used as inoculum. The particles were removed by
sedimentation after 1 day while moderately aerating.
Duration of test (contact time):
28 d
Initial conc.:
1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: The river water used in the Closed Bottle test was spiked per liter of water with
8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.3 mg Na2 HPO4·2H2O, 22.5 mg
MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was
omitted from the medium to prevent nitrification.

TEST SYSTEM
- Culturing apparatus: 0.30 L BOD (biological oxygen demand) bottles with glass stoppers
- Number of culture flasks/concentration: 10 for test substance, 6 for sodium acetate
- Measuring equipment: The dissolved oxygen concentrations were determined electronically using an oxygen electrode (WTW TrioXmatic EO 200) and meter (WTW OXI 530) (Retsch, Ochten, the Netherlands). The pH was measured using a Eutech Cyberscan pH11 pH meter (Eutech Instruments, Nijkerk, the Netherlands). The temperature was measured and recorded with a sensor connected to a data logger.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
Reference substance:
acetic acid, sodium salt
Remarks:
concentration in the bottle: 6.7 mg/L; source: Acros organics
Parameter:
% degradation (O2 consumption)
Value:
4
Sampling time:
7 d
Parameter:
% degradation (O2 consumption)
Value:
13
Sampling time:
14 d
Parameter:
% degradation (O2 consumption)
Value:
83
Sampling time:
21 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
83
Sampling time:
28 d
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Fyrquel EHC PLUS (low TPP) did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. Fyrquel EHC PLUS (low TPP) was biodegraded by 83% at day 28 in the closed bottle test. Hence, this substance should be classified as readily biodegradable.
The test is valid as shown by an endogenous respiration of 1.4 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 90 of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations > 0.5 mg/L in all bottles during the test period.
Executive summary:

Theoretical oxygen demand (ThOD)

The calculated theoretical oxygen demand (ThOD) of Fyrquel EHC PLUS (low TPP)

is 2.3 mg/mg. The ThOD of sodium acetate is 0.78 mg/mg.

Toxicity

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate

by the test substance in the Closed Bottle test was not determined because

possible toxicity of Fyrquel EHC PLUS (low TPP) to microorganisms degrading

acetate is not relevant. Inhibition of the endogenous respiration of the inoculum

by the test substance at day 7 was not detected. The non toxicity was deduced

from the oxygen consumption of 0.1 mg/L at day 7. Therefore, no

inhibition of the biodegradation due to the "high" initial test substance

concentration of 1.0 mg/L is expected. The initial test substance concentration is

high compared to environmental concentrations of organic substances (low μg/L

range).

Test conditions

The pH of the media was 8.0 at the start of the test. The pH of the medium at day

28 was 8.1 (control), 8.0 (controls), and 7.9 (test). Temperatures were within the

prescribed temperature range of 22 to 24°C.

Validity of the test

The validity of the test is demonstrated by an endogenous respiration of

1.4 mg/L at day 28. Furthermore, the differences of the replicate values

at day 28 were less than 20%. The biodegradation percentage of the reference

compound, sodium acetate, at day 14 was 90. Finally, the validity of the test is

shown by oxygen concentrations > 0.5 mg/L in all bottles during the test period.

Biodegradability

Fyrquel EHC PLUS (low TPP) is biodegraded by 83% at day 28 in the Closed Bottle

test (Figure and Tables I-II). The pass level of 60% was reached after 8 days

upon achieving 10% biodegradation. Fyrquel EHC PLUS (low TPP) therefore

fulfilled the 10-day time window criterion. Fyrquel EHC PLUS (low TPP) is

therefore classified as readily biodegradable based on the biodegradation

percentage of 83% at day 28 and the time window of 8 days.

The pass level in ready biodegradability tests using either oxygen consumption or

carbon dioxide evolution is ≥ 60% at day 28. Biodegradation percentages ≥ 60 are interpreted as complete (ultimate) biodegradation. Biodegradation percentages ranging from 60 to ~95% (≥ 100% biodegradation is impossible) are found for all utimately biodegradable substances. The biodegradation percentage of 83% reached at day 21 therefore shows that the biodegradation of Fyrquel EHC PLUS (low TPP) was completed at day 21.

Description of key information

Two studies performed according to the OECD 301D guideline are available.

After 28 days, the biodegradability was 78% and 83% for the multi-constituents containing respectively 4% and 2% TPP.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

Two ready biodegradability tests in which biodegradability was measured in an aerobic aqueous medium were performed, one study with Fyrquel EHC PLUS (van Ginkel 2012a) and another study with Fyrquel EHC PLUS (low TPP) (van Ginkel 2012b) as test substance. The ready biodegradability test was performed in the closed bottle test according to OECD 301 D guideline.

Both test substances did not cause a reduction in the endogenous respiration and are therefore considered to be non-inhibitory to the inoculum. Fyrquel EHC PLUS and Fyrquel EHC PLUS (low TPP) were respectively biodegraded by 78% and 83% at day 28 in the closed bottle test and the validity criteria were fulfilled. Hence, both substances should be classified as readily biodegradable.

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