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Biodegradation in water: screening tests

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biodegradation in water: inherent biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
19 September 2005 to 18 October 2005
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: guideline study under GLP
according to
OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)
according to
EU Method C.9 (Biodegradation: Zahn-Wellens Test)
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: waste water treatment plant ARA Ergolz II, Fuellinsdorf, Switzerland
- Storage length: not indicated
- Sorage condition: aerated at room temperature
- Preparation of inoculum for exposure: washed twice with tap water, supernatant decanted, homogenized and dried
- Pretreatment: none
- Concentration of sludge: 4 g dry weight/L
- Water filtered: no
- Ratio inoculum/test substance (as DOC): 3:1
Duration of test (contact time):
28 d
Initial conc.:
280 mg/L
Based on:
test mat.
Initial conc.:
ca. 100 mg/L
Based on:
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
- Composition of medium: accoding to the guideline
- Test temperature: 21-25 °C
- pH: 6.5-7.6 (measured at start and before each sampling)
- pH adjusted: if necessary to pH 7.1 to 7.9 (both in test substance vessels and controls)
- Aeration of dilution water: yes
- Suspended solids concentration: not determined
- Continuous darkness: yes

- Culturing apparatus: 2000 mL Erlenmeyer with 1000 mL testsolution (water and evaporation losses were compensated if necessary)
- Number of culture flasks/concentration: 2 for test substance, 2 for inoculum controls, 2 for reference controls, 1 toxicity control, 1 sterility control
- Method used to create aerobic conditions: not fully closed vessels and continuously stirring with magnetic stirrer
- Oxygen concentration: 6.7-8.9 mg/L (measured at start and before each sampling)
- Measuring equipment: TOC-analyzer

- Sampling frequency: after 3 hours and on day 3, 7, 10, 14, 21 and 28
- Sampling method: no details
- Sterility check if applicable: included
- Sample storage before analysis: analysed immediately

- Inoculum blank: 2
- Abiotic sterile control: 1
- Toxicity control: 1
Reference substance:
diethylene glycol
Test performance:
All values are corrected for the degradation measured in inoculum controls.
Key result
% degradation (DOC removal)
Sampling time:
3 d
Key result
% degradation (DOC removal)
>= 50 - <= 53
Sampling time:
7 d
Remarks on result:
other: from day 7 to 28
Details on results:
Toxicity controls 74% degradation within 14 days (based on DOC of 190.3 mg/L 49% test substance and 51% reference substance)
No degrdation in abiotic controls
No DOC removal during the first 3 hours of the test --> indicative for no adsorption
Results with reference substance:
The degradation of the reference substance was 100% after 7 days.
Validity criteria fulfilled:
Interpretation of results:
inherently biodegradable
The substance is inherently biodegrdable
Executive summary:

In a Zahn-Wellens/EMPA test a biodegradation of 53% was observed for the substance (initial concentration 280 mg/L).No toxicity was towards micto organism was found. As the degradation is > 35% the substance is considered inherently biodegradable.

Description of key information

In a Zahn-Wellens/EMPA test (RCC 2005) a biodegradation of 53% was observed for the substance (initial concentration 280 mg/L).No toxicity was towards micro-organisms was found. As the degradation is > 35% the substance is considered inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

In addition in a limited reported Zahn-Wellens test (BASF 1988) the substance degraded up to 60%, which confirms the finding that the substance is inherently biodegradable.