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Biodegradation in water: screening tests

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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:
other: GLP guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)
Deviations:
yes
Remarks:
Concentration of test material was reduced to 0.2 and 1.0 mg/L.
GLP compliance:
yes
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: A sample of activated sludge mixed Iiquor was obtained from the Midland Municipal Wastewater Treatment Plant (Midland, Michigan. USA) on April 28, 1997.
- Concentration of sludge: mixed liquor suspended solids (MLSS) concentration of the activated sludge sample was determined to be 2190 ± 160 mg/L: Based on this determination, the mineral medium (3 liters) was inoculated with 41 ml of activated sludge to yield a final MLSS concentration of 30 ± 1 mg/L.


Duration of test (contact time):
28 d
Initial conc.:
0.2 mg/L
Based on:
test mat.
Initial conc.:
1 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 23 ± 1°C
- pH adjusted: yes, the pH of the inoculated mineral medium was adjusted from 7.01 to 7.37 with 5N NaOH.

TEST SYSTEM
- Culturing apparatus: 1 L flasks were sealed with rubber stoppers fitted with CO2 traps containing 4 ml of 1N NaOH.


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes
- Toxicity control: yes
- Other: non labelled control

Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
33.5
St. dev.:
1.5
Sampling time:
3 d
Remarks on result:
other: 0.2 mg [14C]-OPP
Parameter:
% degradation (CO2 evolution)
Value:
62.5
St. dev.:
0.5
Sampling time:
11 d
Remarks on result:
other: 0.2 mg [14C]-OPP
Parameter:
% degradation (CO2 evolution)
Value:
70.8
St. dev.:
0.3
Sampling time:
28 d
Remarks on result:
other: 0.2 mg [14C]-OPP
Parameter:
% degradation (CO2 evolution)
Value:
35.2
St. dev.:
0.2
Sampling time:
3 d
Remarks on result:
other: 1.0 mg [14C]-OPP
Parameter:
% degradation (CO2 evolution)
Value:
67.7
St. dev.:
0.8
Sampling time:
11 d
Remarks on result:
other: 1.0 mg [14C]-OPP
Parameter:
% degradation (CO2 evolution)
Value:
75.7
St. dev.:
0.5
Sampling time:
28 d
Remarks on result:
other: 1.0 mg [14C]-OPP
Details on results:
70.8 and 75.7% biodegradation (CO2 formation as percentage of theoretical value) after 28 days at low (0.2 mg/L) and high (1.0 mg/L) concentration
Results with reference substance:
Kinetic of control substance: 81% after 2 days

Biodegradation rates of o-phenylphenol (percentage of added radioactivity mineralized to 14CO2):

 

Day

Abiotic control

Biodegradation at different OPP concentrations

1.0 mg [14C]-OPP

0.2 mg [14C]-OPP

1.0 mg [14C]-OPP

0

0.0%

0.0%

0.0%

3

0.2%

33.5% (± 1.5)

35.2% (± 0.2)

11

0.3%

62.5% (± 0.5)

67.7% (± 0.8)

28

0.6%

70.8% (± 0.3)

75.7% (± 0.5)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to analogue justification provided in IUCLID section 13
Reason / purpose for cross-reference:
read-across source
Parameter:
% degradation (CO2 evolution)
Value:
75.7
St. dev.:
0.5
Sampling time:
28 d
Remarks on result:
other: 1.0 mg [14C]-OPP
Interpretation of results:
readily biodegradable

Description of key information

Readily biodegradable: 70.8 – 75.7% in 28 days (OECD 301B); read across

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Reliable experimental data on the biodegradability of sodium 2-biphenylate are not available. The assessment was therefore based on a study conducted with the analogue substance 2-phenylphenol (CAS 90-43-7). The read across approach is in accordance with Regulation (EC) No. 1907/2006, Annex XI, 1.5. Please refer to the analogue justification attached to IUCLID section 13 for a detailed justification.

The biodegradability of the source substance 2-phenylphenol (CAS 90-43-7) was tested according to OECD 301B under GLP conditions using non-adapted activated sludge as inoculum (Gonsior and Tryska, 1997). To avoid potential inhibitory effects the tested substance, concentrations were lower than specified in the guideline (i.e. 0.2 mg and 1 mg test material/L). The test substance was radiolabelled (14C-OPP) and the degradation was followed by measuring the amount of evoluted14CO2. Furthermore the concentration of the test substance was determined at day 28 by HPLC. Based on the CO2evolution a biodegradation rate of 70.8% was determined at a test substance concentration of 0.2 mg/L. The determined degradation rate at a substance concentration of 1 mg/L was 75.7%.The 10-day window was met (degradation rate at day 11: > 60%). Thus the substance is considered as readily biodegradable.

The results are supported by data available for sodium 2-biphenylate. The ready biodegradability of the substance was tested based on the oxygen consumption in a study design similar to OECD 301D (Hamburger, 1976). At a test substance concentration of 2.4 mL/L a degradation rate of 84% was determined after 20 days. The results were not considered for assessment because of insufficient study documentation. However, the results are a further indication of a ready biodegradability of the substance.

Based on the results for the source substance (in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5) sodium 2-biphenylate is considered as readily biodegradable.