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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:
19 Apr - 17 May 2000
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Remarks:
Niedersächsiches Umweltministerium, Hannover, Germany
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of inoculum/activated sludge: Sewage treatment plant Hildesheim, Germany
- Laboratory culture: no
- Pretreatment: Filtered with folded filter without using the first 200 mL of the filtrate. The second filtrate effluent from the domestic waste water is used to initiate inoculation.
- Colony forming units: 9.2E+07 CFU/L (inoculum); 6.1E+04 CFU/L (in test vessel)
Duration of test (contact time):
28 d
Initial conc.:
4 mg/L
Based on:
test mat.
Initial conc.:
8.32 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
TEST CONDITIONS
- Composition of medium: according to guideline
- Test temperature: 20.5 - 21.0 °C
- pH: 7.45 - 7.56 (begin), 7.25 - 7.64 (end)
- pH adjusted: no
- Aeration of dilution water: One day before medium preparation the dilution water was aerated until oxygen saturation and then left at room temperature for at least 20 h.

TEST SYSTEM
- Culturing apparatus: BOD bottles with glass stoppers, 300 mL test volume
- Number of culture flasks/concentration: 10
- Method used to create aerobic conditions: The dilution water was aerated until oxygen saturation.
- Measuring equipment: Oximeter, WTW Oxi 530
- Test performed in closed vessels: yes
- Other: Test solutions were made as stock solutions. 0.2 mL of the inoculum was given in each BOD bottle.

SAMPLING
- Sampling frequency: on day 0, 7, 14, 21 and 28
- Sampling method: Oxygen concentration was measured in the incubation vessels.

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 10 bottles
- Toxicity control: yes, 10 bottles
- Other: Reference substance: yes, 10 bottles
Reference substance:
acetic acid, sodium salt
Key result
Parameter:
% degradation (O2 consumption)
Value:
68
Sampling time:
28 d
Details on results:
The 10-day window was reached (10% degradation after 4 d and 69% after 14 d). Thus, the test substance can be regarded as readily biodegradable according to the OECD criteria. The toxicity control attained 42% after 14 d. Since more than 25% biodegradation occurred, the test substance is not inhibitory to the inoculum.
Results with reference substance:
80% after 21 d, 60% pass level was reached.

Table 1: Degradation of the test substance, reference substance and toxicity control.

Sampling day

Test substance [%]

Reference substance [%]

Toxicity control [%]

7

21

78

27

14

69

79

42

21

65

80

52

28

68

74

48

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The tested substance is readily biodegradable (68% after 28 d) under tested conditions (OECD 301D) and the 10-day window criterion was met.
Executive summary:

The ready biodegradability of the substance by domestic, non-adapted activated sludge was performed according to the OECD guideline 301 D and GLP. The test was run for 28 days and microorganisms were exposed to 4 mg/L test material corresponding to 8.32 mg/L ThOD/L. O2 consumption was followed for the estimation of the biodegradation. Acetic acid (10 mg/L) was used as a reference substance. A toxicity control was set up with 2 mg/L test item and 5 mg/L reference substance in order to examine the toxicity of the tested substance on microorganisms. 68% biodegradation took place after 28 d, the 10-day window criterion was fulfilled and therefore the tested substance is considered to be readily biodegradable. The toxicity control attained 42% degradation after 14 d, verifying that the tested item was not inhibitory to the inoculated microorganisms.

Description of key information

Readily biodegradable: 68% biodegradation after 28 d, 10-day window criterion met (OECD 301 D). 

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

One study is available, testing the ready biodegradability of the substance by domestic, non-adapted activated sludge. The test was performed according to the OECD guideline 301 D and GLP. The test was run for 28 days and microorganisms were exposed to 4 mg/L test material corresponding to 8.32 mg/L ThOD/L. O2 consumption was followed for the estimation of the biodegradation. Acetic acid (10 mg/L) was used as a reference substance. A toxicity control was set up with 2 mg/L test item and 5 mg/L reference substance in order to examine the toxicity of the tested substance on microorganisms. 68% biodegradation took place after 28 d, the 10-day window criterion was fulfilled and therefore the tested substance is considered to be readily biodegradable. The toxicity control attained 42% degradation after 14 d, verifying that the tested item was not inhibitory to the inoculated microorganisms.