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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
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Principles of method if other than guideline:
Two concentrations of n-nitrosodiphenylamine (5 and 10 mg/L) were added to a culture medium containing domestic water inoculum. Degradability was assessed by both DOC and TOC methods after 7 days. In addition, it was followed by 3 weekly subcultures. In brief, a sample of the activated inoculum of the preceding incubation flasks was added to new flasks containing fresh incubation medium and both concentration of test-item (5 and 10 mg/L). After 7 days, biodegradability was assessed and so on.
GLP compliance:
no
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
No data
Duration of test (contact time):
7 d
Initial conc.:
5 mg/L
Based on:
DOC
Initial conc.:
10 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Parameter followed for biodegradation estimation:
TOC removal
Details on study design:
TEST CONDITIONS
- Solubilising agent (type and concentration if used): ethanol, concentration not mentioned
- Test temperature: 25°C
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Erlenmeyer flask
- Number of culture flasks/concentration: 3 per concentration
- Method used to create aerobic conditions: static, cotton stoppered
- Measuring equipment: GC
- Test performed in closed vessels due to significant volatility of test substance: no

SAMPLING
- Sampling frequency: once a week
- Sampling method: not mentioned
- Sample storage before analysis: not mentioned


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes

STATISTICAL METHODS: not mentioned
Reference substance:
other: phenol
Parameter:
other: DOC or TOC removal
Value:
87
Sampling time:
7 d
Remarks on result:
other: 1st flask (1st week) - 5 mg/L
Parameter:
other: DOC or TOC removal
Value:
100
Sampling time:
7 d
Remarks on result:
other: 2nd flask (2nd week) - 5 mg/L
Parameter:
other: DOC or TOC removal
Value:
92
Sampling time:
7 d
Remarks on result:
other: 3rd flask (3rd week) - 5 mg/L
Parameter:
other: DOC or TOC removal
Value:
100
Sampling time:
7 d
Remarks on result:
other: 4th flask (4th week) - 5 mg/L
Parameter:
other: DOC or TOC removal
Value:
47
Sampling time:
7 d
Remarks on result:
other: 1st flask (1st week) - 10 mg/L
Details on results:
%degr - 1st flask - 10 mg/L: 43%
%degr - 2nd flask - 10 mg/L: 63%
%degr - 3rd flask - 10 mg/L: 95%
%degr - 4th flask - 10 mg/L: 98%
Results with reference substance:
Phenol was biodegraded at 100% or almost 100% (>96%) for both concentrations in all trials.
Validity criteria fulfilled:
not applicable
Interpretation of results:
inherently biodegradable
Conclusions:
Based on the results, the substance is considered inherently biodegradable.
Executive summary:

Biodegradability of n-nitrosodiphenylamine was recorded according to a non standard method. Two concentrations of n-nitrosodiphenylamine (5 and 10 mg/L) were added to a culture medium containing domestic water inoculum. Degradability was assessed by both DOC and TOC methods after 7 days. In addition, it was followed by 3 weekly subcultures. In brief, a sample of the activated inoculum of the preceding incubation flasks was added to new flasks containing fresh incubation medium and both concentration of test-item (5 and 10 mg/L). After 7 days, biodegradability was assessed and so on.

After 7 days, the smallest biodegradation was 47% and the highest was 100%. The test-item is considered inherently biodegradable and not readily biodegradable because a study on degradation simulation in soil showed that nitrosodiphenylamine is not rapidly biodegradable (half-life of 45 days at 12°C).

Description of key information

Although some degradation can be observed, nitrosodiphenylamine is not readily biodegradable. This substance is however inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information