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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
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): secondary effluent are withdrawn on November 29th, 2017 from the sewage treatment plant Ruhrverband Kläranlage, Sunthelle 6, 57392 Schmallenberg, Germany, which is mainly fed with municipal wastewater

The samples were kept aerobic during transport to the laboratory. The samples were allowed to settle for 1 hour and filtered through a coarse filter paper. The inoculum was kept aerobic until required. The concentration used in the test was 1 mL/L.
Duration of test (contact time):
28 d
Initial conc.:
2 mg/L
Based on:
act. ingr.
Initial conc.:
5 mg/L
Based on:
act. ingr.
Initial conc.:
1.4 mg/L
Based on:
ThOD
Initial conc.:
3.6 mg/L
Based on:
ThOD
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: OECD mineral medium
- Additional substrate: no
- Test temperature: 20°C
- pH: 7.4 ± 0.2
- pH adjusted: no
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 300 mL test vessels
- Number of culture flasks/concentration: 16
- Method used to create aerobic conditions: strongly aerated for 20 minutes and allowed to stand for 20 h at test temperature
- Measuring equipment: O2 electrode

SAMPLING
- Sampling frequency: test start and at day 2, 5, 7, 9, 14, 21, and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: The blank control consisted of inoculated mineral medium only, 16 vessels
- Abiotic sterile control: no
- Toxicity control: A toxicity control containing test item at 5 mg per litre and reference item at 2 mg per litre mineral test medium was applied, 8 vessels
- Procedural control: 16 vessels containing reference item (5 mg/L) and inoculum


Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (O2 consumption)
Value:
0
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Remarks:
toxicity control
Value:
28
Sampling time:
14 d
Details on results:
The biodegradation of the test item after 28 days of incubation in the static test was found to be 0 % in the assays with 2 mg/L and 5 mg/L. Thus, no biodegradation within a 10-day-window could be obtained.
The biodegradation of the item mixture in the toxicity control was found to be 28 % after 14 days of incubation. Thus, the demanded threshold value of 25 % is exceeded and the test item can be identified as non-toxic in a ready biodegradability test.
Results with reference substance:
The reference item sodium benzoate was degraded to 72 % within the first 14 days.

Degradation (%) after 14 days.

Single and mean values of the parallel test vessels and standard deviation.

vessel

Test
suspension A

Test
suspension B

Procedural
control

Toxicity
control

1

-7.5

-10.6

69.8

28.3

2

-15.9

-9.6

68.9

27.2

Mean

-11.7

-10.1

69.3

27.7

SD

5.9

0.7

0.6

0.8

 

Degradation (%) after 28 days.

Single and mean values of the parallel test vessels and standard deviation.

vessel

Test
suspension A

Test
suspension B

Procedural
control

Toxicity
control

1

-9.3

-4.0

53.2

24.6

2

-2.0

-7.6

53.3

23.4

Mean

-5.7

-5.8

53.3

24.0

SD

5.2

2.5

0.0

0.8

 

Validity criteria:

The Closed Bottle Test fulfills the validity criteria of the guideline:

With 7% the difference of extremes of replicate values of the removal of the test item at the end of the test was less than 20 %.

The percentage degradation of the reference item has exceeded the pass level of 60 % by day 14.

The oxygen depletion in the inoculum blank did not exceed 1.5 mg/L after 28 days.

The oxygen concentration in the test vessels did not fall below 0.5 mg/L at any time.

Validity criteria fulfilled:
yes
Interpretation of results:
under test conditions no biodegradation observed
Conclusions:
Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid is not readily biodegradable under the chosen test conditions. No inhibitory effects of the test item were observed (more than 25 % degradation occurred within 14 days) in the toxicity control.
Executive summary:

The biodegradation of Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid was investigated over a 28-day period in a Closed Bottle Test according to OECD guideline 301 D and EU method C.4-E. The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The test solutions were incubated in closed flasks at 20 °C ± 1 °C for 28 days. The rate of degradation was monitored by measuring the decrease of oxygen in the medium over a 28-d period. The amount of oxygen taken up by the microbial population during biodegradation of the test item at a concentration of 2 mg/L (ThOD = 1.44 mg/L) and 5 mg/L (ThOD = 3.60 mg/L), respectively, corrected for uptake by the blank inoculum run in parallel, was expressed as a percentage of the ThOD (theoretical oxygen demand). In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 2 mg/L, along with a toxicity control at 5 mg/Ltest itemand 2 mg/L sodium benzoate.

The biodegradation of Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid in the static test was found to be 0 % for a concentration of 2 mg test item per liter and 5 mg test item per liter after 28 days.Thus, no biodegradation within a 10-day-window could be obtained.

The degradation of the reference substance sodium benzoate had reached 72 % within the first 14 days. The difference of extremes of replicate values of the removal of the test item at the end of the test is less than 20%. Therefore, the test can be considered as valid.

Slight inhibitory effects of the test item were observed (28 % degradation occurred within 14 days) in the toxicity control.

Therefore, Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid must be considered as not readily biodegradable under the chosen test conditions.

Description of key information

not readily biodegradable (OECD TG 301D, RL1, GLP)

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

The biodegradation of Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid was investigated over a 28-day period in a Closed Bottle Test according to OECD guideline 301 D and EU method C.4-E. The test medium was inoculated with microorganisms from a digester of a sewage treatment plant mainly fed with municipal wastewater.

The test solutions were incubated in closed flasks at 20 °C ± 1 °C for 28 days. The rate of degradation was monitored by measuring the decrease of oxygen in the medium over a 28-d period. The amount of oxygen taken up by the microbial population during biodegradation of the test item at a concentration of 2 mg/L (ThOD = 1.44 mg/L) and 5 mg/L (ThOD = 3.60 mg/L), respectively, corrected for uptake by the blank inoculum run in parallel, was expressed as a percentage of the ThOD (theoretical oxygen demand). In order to check the procedure, sodium benzoate was used as a degradable reference item at a concentration of 2 mg/L, along with a toxicity control at 5 mg/Ltest itemand 2 mg/L sodium benzoate.

The biodegradation of Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid in the static test was found to be 0 % for a concentration of 2 mg test item per liter and 5 mg test item per liter after 28 days.Thus, no biodegradation within a 10-day-window could be obtained.

The degradation of the reference substance sodium benzoate had reached 72 % within the first 14 days. The difference of extremes of replicate values of the removal of the test item at the end of the test is less than 20%. Therefore, the test can be considered as valid.

No inhibitory effects of the test item were observed (more than 25 % degradation occurred within 14 days) in the toxicity control.

Therefore, Reaction product of lauryl-PDA/lauryl-DETA with chloroacetic acid must be considered as not readily biodegradable under the chosen test conditions.

However, in a STP simulation test (OECD TG 303 A) a mean daily degradation rate of 75% (ultimate degradation) was observed (see section simulation tests).

[Type of water: freshwater]