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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:
guideline study without detailed documentation
Qualifier:
according to guideline
Guideline:
OECD Guideline 310 (Ready Biodegradability - CO2 in Sealed Vessels (Headspace Test)
GLP compliance:
no
Remarks:
The study was not performed according to GLP. However, the quality of the test carried out in this laboratory is highly reliable, with experimental conditions rigorously similar to those recommended in the OECD guidelines.
Oxygen conditions:
aerobic
Inoculum or test system:
sewage, predominantly domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): inoculum taken from the aeration tank of a full-scale wastewater treatment plant which treats predominantly domestic sewage (ETE Jundiai-SP/Brazil)
- Method of cultivation: The activated sludge was treated by allowing to settle three times for 30 minutes. For each settling the supernatant was rejected and the solids were redispersed in the mineral medium. In order to lower organic carbon content and to reduce the blank CO2 evolution, the activated sludge was aerated overnight.
- Initial cell/biomass concentration: 1g/L dry weight
Duration of test (contact time):
28 d
Initial conc.:
20.15 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
CO2 evolution
Details on study design:
TEST CONDITIONS
- Composition of medium: medium prepared according to OECD guideline 301B

TEST SYSTEM
- Culturing apparatus: serum bottles 120 mL capacity, sealed with butyl rubber septa and aluminium crimp seals.
- Number of culture flasks/concentration: 15 blanks, 15 test item, 15 reference item, 4 inhibition
- Measuring equipment: Shimadzu Model TOC 5000 inorganic carbon analyser
- Test performed in open system: no
- Details of trap for CO2 and volatile organics if used: 1mL NaOH injected into test bottles


SAMPLING
- Sampling frequency: samples taken on days 2, 5, 7, 14, 21 and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
- Other: reference item
Reference substance:
benzoic acid, sodium salt
Parameter:
% degradation (CO2 evolution)
Value:
78.55
Sampling time:
5 d
Parameter:
% degradation (CO2 evolution)
Value:
82.42
Sampling time:
7 d
Parameter:
% degradation (CO2 evolution)
Value:
83.77
Sampling time:
14 d
Parameter:
% degradation (CO2 evolution)
Value:
86.46
Sampling time:
21 d
Parameter:
% degradation (CO2 evolution)
Value:
87.74
Sampling time:
28 d
Results with reference substance:
89.42% after 5 days, 95.06% after 7 days
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Executive summary:

An experimental study with the reaction mass was conducted to assess the readily biodegradability according to the OECD guideline 310. Predominantly domestic sewage sludge (adapted) were exposed to an initial test item concentration of 20.15 mg/l DOC for 28 d in a closed system under aerobic conditions. The degradation of the test item was measured as CO2 evolution over the time of the test. After 7 days 95.06 % of the initial amount were degraded and the 10-day window criterion was met. Therefore, the test item can be considered as readily biodegradable according to OECD criteria.

Description of key information

The reaction mass is readily biodegradable (according to OECD criteria)

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable
Type of water:
freshwater

Additional information

An experimental study with the reaction mass was conducted to assess the readily biodegradability according to the OECD guideline 310. Predominantly domestic sewage sludge (adapted) were exposed to an initial test item concentration of 20.15 mg/l DOC for 28 d in a closed system under aerobic conditions. The degradation of the test item was measured as CO2 evolution over the time of the test. After 7 days 95.06 % of the initial amount were degraded and the 10-day window criterion was met. Therefore, the test item can be considered as readily biodegradable according to OECD criteria (Rhodia, 2009).


This result was confirmed by the three supporting studies (MITI 1992, MITI 1992 and BASF AG 1998) which assessed the biodegradability of the single components of the reaction mass. In all studies the compounds were considered as readily biodegradable.

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