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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:
16 May to 14 June 2013
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
the Study was performed according to OECD guideline 301F under GLP without modification of the Guideline
Qualifier:
according to
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
Not applicable
GLP compliance:
yes (incl. certificate)
Remarks:
GLP Compliance Statement (Registration No. CNAS GLP 0002) Laboratory of Ecotoxicity & Environmental Safety, Guangdong Detection Center of Microbiology, Guangdong China, is inspected to principles of GLP published by OECD. Date of Expiry: 2013-11-23
Specific details on test material used for the study:
- Description: pale yellow liquid
- pH 5.4
- Melting point: 9°C (Freezing point)
- Boiling point: 266°C
-Vapour pressure : 0.11Pa (25°C)
- Solubility in water : 0.051 g/L
- Partition coefficient: .Log Pow=3.12
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Remarks:
The WWTP is not specifically mentioned as predominantly domestic but this is assumed from the provenance statement "Liede Sewage Treatment Plant of Guangzhou"
Details on inoculum:
- Source: Liede Sewage Treatment Plant of Guangzhou
-Batch N° IAs20130513-1
- The inoculum is recommended by "the Guidelines for the Testing of Chemicals".
- The sludge was washed by centrifugation, the supernatant liquid phase was decanted and the solid material resuspended in a mineral medium. A homogenized aliquot of the final sludge suspension was weighted. Based on this ratio, calculated amount of wet sludge was resuspended in a mineral medium to obtain a concentrtaion equivalent to 2.4 g dry material per liter. Appropriate volume of inoculum was inoculated in each botle to give a final concentration of 28 mg dru material per liter.
Duration of test (contact time):
28 d
Initial conc.:
19 mg/L
Based on:
other:
Remarks:
Bottle 1,2 and A (test suspension): containing test substance, inoculum and test medium
Initial conc.:
20 mg/L
Based on:
other:
Remarks:
Bottle 6 (toxicity control): containing test substance, reference substance, inoculum and test medium
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
Test conditions:
The test bottles were agitated and aereted on OxiTop® Control BOD at 22°C+/-1°C in the dark over 28 days period.
Reference substance:
benzoic acid, sodium salt
Remarks:
33 mg/L
Preliminary study:
None
Key result
Parameter:
% degradation (O2 consumption)
Value:
34.7
Sampling time:
28 d
Remarks on result:
other: Not readily biodegradable
Details on results:
At the end of the test, the oxygen uptake of the two inoculum blanks were 38.2 mg/L and 33.7 mg/L.
At the end of the test, pH values of test suspensions were 7.46 and 7.52, those of inoculum blanks were 7.26 and 7.27, and pH values of the procedure control and toxicity control were 7.59 and 7.58.
On the 14th day of the test, the percentage biodegradation of the reference substance and toxicity control were 71.9% and 65.0%, which showed that inoculum activity could meet the requirement of the test, and the test material was considered not to have a toxic effect on the sewage sludge micro-organisms used in the study.
Under the test conditions, the percentage biodegradation of the test substance were 36.0%, 35.0% (two replicates) and 35.5% (Mean) on the 14d and 37.9%, 31.5% (two replicates) and 34.7% (mean) on the 28d.
Results with reference substance:
The percentage degradation (based on ThOD) of reference substance and toxicity control were 71.9% and 65.0% which had reached the pass levels of 60% and 25% by day 14.

See attached background material section for results- table

Validity criteria fulfilled:
yes
Interpretation of results:
not readily biodegradable
Conclusions:
The mean percentage biodegradation of the test substance ST 01C 11 was 34.7% after 28d, therefore the substance cannot be considered readily biodegradable under the present test conditions.
Executive summary:

The ready biodegradability of the test substance has been determined by the Manometric Repirometry Test according to the OECD Guideline No. 301F with GLP compliance. the ready biodegradability test of the test substance was conducted with unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28 day period.

At the end of the test, the oxygen uptake of the two inoculum blanks were 38.2 mg/L and 33.7 mg/L.

At the end of the test, pH values of test suspensions were 7.46 and 7.52, those of inoculum blanks were 7.26 and 7.27, and pH values of the procedure control and toxicity control were 7.59 and 7.58.

On the 14th day of the test, the percentage biodegradation of the reference substance and toxicity control were 71.9% and 65.0%, which showed that inoculum activity could meet the requirements of the test, and the test material was considered not to have a toxic effect on the sewage sludge micro-organisms used in the study.

Under the test conditions, the percentage biodegradation of the test substance were 36.0%, 35.0% (two replicates) and 35.5% (Mean) on the 14d and 37.9%, 31.5% (two replicates) and 34.7% (mean) on the 28d. Therefore the substance cannot be considered readily biodegradable under the present test conditions.

Description of key information

OECD Guideline 301F, GLP, key study, validity 1:

34.7% biodegradation was observed after 28 days, so the substance cannot be considered rapidly biodegradable, according to CLP Regulation No 1272/2008

Key value for chemical safety assessment

Biodegradation in water:
under test conditions no biodegradation observed

Additional information

One valid key study is available (Yanzhen and Chengfang, 2013) to assess the readily biodegradation of the registered substance.

The ready biodegradability of the test substance has been determined by the Manometric Repirometry Test according to the OECD Guideline No. 301F with GLP compliance. The ready biodegradability test of the test substance was conducted with unacclimatised sewage micro-organisms by measuring oxygen consumption over the 28 -day period.

At the end of the test, the oxygen uptake of the two inoculum blanks were 38.2 mg/L and 33.7 mg/L.

At the end of the test, pH values of test suspensions were 7.46 and 7.52, those of inoculum blanks were 7.26 and 7.27, and pH values of the procedure control and toxicity control were 7.59 and 7.58.

On the 14d of the test, the percentage biodegradation of the reference substance and toxicity control were 71.9% and 65.0%, which showed that inoculum activity could meet the requirement of the test, and the test material was considered not to have a toxic effect on the sewage sludge micro-organisms used in the study.

Under the test conditions, the percentage biodegradation of the test substance were 36.0%, 35.0% (two replicates) and 35.5% (Mean) on the 14d and 37.9%, 31.5% (two replicates) and 34.7% (mean) on the 28d. Therefore the substance cannot be considered readily biodegradable under the present test conditions.

Another biodegradation study was performed on mimosal according to OECD 301F guideline (Miffon, 2012). At the end of the study, 48% of biodegradation was observed after 28 days.This study was scored klimish 3 because of negative biodegradation during a long lag time (12 days): it suggests an inhibition of bacterial during this period as the concentration tested (100.1 mg/L) is higher than the EC20 of ASRIT test (58 mg/L). Nevertheless, the biodegradation is higher than the one from the key study of Yanzhen and Chengfang (2013) where only 34.7% of biodegradation was measured.

In both studies, the substance cannot be considered readily biodegradable under the present test conditions.