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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Administrative data

Endpoint:
biodegradation in water: sediment simulation testing
Data waiving:
study scientifically not necessary / other information available
Justification for data waiving:
other:
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Reason / purpose:
data waiving: supporting information
Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
From16 July , 2014 to 15 September, 2014
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
yes
Remarks:
minor: Ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).
Qualifier:
according to
Guideline:
ISO DIS 9408 (Ultimate Aerobic Biodegradability - Method by Determining the Oxygen Demand in a Closed Respirometer)
Deviations:
yes
Remarks:
minor: Ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
minor: Ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
River water was sampled from the Rhine near Heveadorp, The Netherlands (10-07-2014). The nearest plant (Arnhem-Zuid) treating domestic waste water biologically was 3 km upstream. The river water was aerated for 7 d before use to reduce the endogenous respiration. River water without particles was used as inoculum. The particles were removed by sedimentation after 1 d while moderately aerating. The inoculum was not pre-adapted to the test substance.
Duration of test (contact time):
ca. 60 d
Initial conc.:
4 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test bottles
The test was performed in 0.30 L BOD (biological oxygen demand) bottles with glass stoppers.

Nutrients, stocks and administration
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 Na2HPO4.2H2O, 22.5 mgMgSO4.7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3.6H2O. Ammonium chloride was not added to the river water to prevent nitrification. Test substance was administered using a stock emulsion prepared in deionized water with polyalkoxylate alkylphenol both at a concentration of 1.0 g/L. Additional control bottles contained polyalkoxylate alkylphenol. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L.

Test procedures
Use was made of 10 bottles containing only river water, 6 bottles containing river water and sodium acetate, 10 bottles containing river water with test substance and surfactant, and 10 bottles containing river water with surfactant. The concentrations of the test substance, surfactant and sodium acetate in the bottles were 4.0, 4.0 and 6.7 mg/L, respectively. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at Day 7, 14, 21, and 28. The Closed bottle test was prolonged by measuring the course of the oxygen decrease in the bottles of Day 28 using a special funnel and oxygen electrode.
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 25
Sampling time:
28 d
Key result
Parameter:
% degradation (O2 consumption)
Value:
ca. 46
Sampling time:
60 d
Details on results:
Theoretical oxygen demand (ThOD)
The calculated theoretical oxygen demand (ThOD) of the main component was 1.9 mg/mg. All other components present in the test substance (information of the sponsor) do have comparable ThODs. The ThOD of sodium acetate was 0.8 mg/mg.

Toxicity
Inhibition of the degradation of a well-degradable compound, sodium acetate by the test substance in the closed bottle test was not determined because possible toxicity of test substance to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial concentration of the test substance is expected.

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 7.9 (controls) and 7.8 (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 1.5 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 substance, sodium acetate, at Day 14 was 83. Finally, the validity of the test was shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Biodegradability
The test substance was biodegraded by 25% at Day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this substance was biodegraded by 46% at Day 60. These results demonstrate that the test substance is inherently biodegradable.
Results with reference substance:
The biodegradation percentage of the reference substance, sodium acetate, at Day 14 was 83.

Table 1: Oxygen consumption (mg/L) and the percentages biodegradation of the test Substance (BOD/ThOD) and reference substance (BOD/ThOD) in the Closed Bottle test

Time (d)

Oxygen consumption (mg/L)

Biodegradation (%)

Test substance

Reference substance

Test substance

Reference substance

0

0.0

0.0

0

0

7

0.3

4.2

4

78

14

0.4

4.5

5

83

21

0.8

 

11

 

28

1.8

 

25

 

42

1.8

 

25

 

60

3.5

 

46

 

Validity criteria fulfilled:
yes
Interpretation of results:
other: Not readily biodegradable, but results on Day 60 indicate inherent biodegradation potential
Conclusions:
Under the conditions of the study, the test substance is not readily biodegradable, but can be considered to be inherently biodegradable.
Executive summary:

A study was conducted to determine the inherent biodegradability of the test substance according to an extended version of OECD Guideline 301D (prolonged closed bottle test) , in compliance with GLP. The test was performed in 0.30 L BOD (biological oxygen demand) bottles with glass stoppers. There were 10 bottles containing only river water, 6 bottles containing river water and sodium acetate, 10 bottles containing river water with test substance and surfactant, and 10 bottles containing river water with surfactant. The concentrations of test substance, surfactant and sodium acetate in the bottles were 4.0, 4.0 and 6.7 mg/L, respectively. No reduction in the endogenous respiration was observed at Day 7. The test substance was therefore considered to be non-inhibitory to the inoculum. The test was valid, as shown by an endogenous respiration of 1.5 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 83% of its theoretical oxygen demand after 14 d. Oxygen concentrations remained >0.5 mg/L in all bottles during the test period. The test substance was biodegraded by 25% at Day 28 and by 46% at Day 60. Under the conditions of the study, the test substance can therefore be considered inherently biodegradable (Ginkel, 2014).

Reason / purpose:
data waiving: supporting information
Reference

Water solubility was determined according to OECD Guideline 105 (Jeuniaux, 2012) as well as using QSAR models from EPISuite v.4.11 (US EPA, 2018).

Water solubility:
156 mg/L
at the temperature of:
25 °C

Experimental value for di-TMPTTA (major constituent):15 mg/L at 25°C 

Predicted values (EPI Suite v.4.11):

WSKOWWIN v.1.43: Water solubility (WS) range: 1.52E-12 to 3142 mg/L at25°C; weighted average:7 mg/L at 25°C.

WATERNT v.1.02: WS range:1.29E-06 to 2.82E+05 mg/L at25°C; weighted average:156 mg/Lat 25°C

The test substance is overall considered to be of low water solubility as evidenced from the experimentally determined water solubility value for the major constituent as well as the ecotox studies (leading to handling the test concentrations as WAFs).

However, in the absence of experimental WS data for all constituents, predicted values were generated to get an idea about the potential WS differences across the different constituents. Based on the predictions, the range of WS values were too wide and the highest values corresponded to two constituents: di-TMPMA and di-TMPDA, both of which are present at very low concentrations (i.e., <5% typical concentrations); therefore these values, even though represent worst case have not been taken forward for risk assessment. Instead the weighted average values, which in this case is closer to the observed experimental WS value as well as the solubilities observed in ecotox studies, has been considered further for hazard as well as risk assessment.

As a conservative approach, the higher weighted average value of 156 mg/L at 25°C has been considered further for risk assessment.

Data source

Materials and methods

Results and discussion

Applicant's summary and conclusion