Producto P0310

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

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:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): wastewater treatment plant (ARA Ergolz II, Füllinsdorf, Switzerland)
- Preparation of inoculum for exposure:
The sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.

Based on this ratio, calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (±10%) dry material per liter. During the holding period of four days, the sludge was aerated at room temperature. Before use, the dry weight of this diluted activated sludge was determined again, and defined amounts were added to test water to obtain a final concentration of 30 mg dry material per liter.

Duration of test (contact time):

ca. 28 d

Initial conc.:

ca. 25.1 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Test temperature: 21 - 24 ºC
- pH: The pH measured in all flasks at the end of exposure (Day 28) was 7.3 – 7.5
- Continuous darkness: The test flasks were incubated in a dark room.

TEST SYSTEM
- Culturing apparatus: 2000-mL Erlenmeyer flasks
- Number of culture flasks/concentration: two
- Other: Each flask was loosely covered with aluminum foil to allow the exchange of air between the flask and the surrounding atmosphere. The test media were continuously stirred by magnetic stirrers.

SAMPLING
One sample of about 10 mL was taken from each test flask per sampling date. Prior to sampling, water evaporation losses were determined by weighing the flasks and were compensated by adding purified water. Deposits on the test vessels were resuspended.
Sampling dates:
Test item and inoculum control: Exposure Day 0, 3, 7, 10, 13, 21 and 28
Procedure control: Exposure Day 0, 3, 7, 13 and 28
Toxicity control: Exposure Day 0, 7, 13 and 28

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Toxicity control: yes

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (DOC removal)

Value:

4

Sampling time:

28 d

Details on results:

In the test flasks, containing the test item and activated sludge (inoculum), the mean concentration of DOC (dissolved organic carbon) varied between 23 and 27 mg/L over the exposure period of 28 days, and was not significantly different from the initial mean DOC concentration of 25 mg/L, measured on Day 0. Expressed as percentage DOC-removal, mean values in the range from -6 to 8% were noted. Therefore, the test substance was not biodegradable under the test conditions within 28 days.

Results with reference substance:

The reference item sodium benzoate was completely biodegraded (100%) within seven days of exposure, thus confirming suitability of the activated sludge.

In the toxicity control, containing the test item (corresponding to 48% of total DOC), the reference item (corresponding to 52% of total DOC) and activated sludge (inoculum), the initial DOC concentration of 56 mg/L measured on Day 0 decreased to 25 mg/L on Day 13. Biodegradation amounted to 55% within 13 days of exposure. Thus, according to the test guidelines, it is assumed that the test item is not inhibitory to activated sludge at the tested concentration of 82 mg/L because degradation was >35% within 14 days.

Validity criteria fulfilled:

yes

Remarks:

(the test item is not inhibitory to activated sludge at the tested concentration because degradation was >35% within 14 days; the reference item was completely biodegraded within 7 days)

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The test substance was not biodegradable under the test conditions within 28 days.

Executive summary:

The test item was investigated for its ready biodegradability in a "28-Day DOC Die-Away Test" according to EU Commission Directive 92/69 EEC, C.4-A (1992) and OECD Guideline for Testing of Chemicals, No. 301 A (1992). In the test flasks, containing the test item and activated sludge (inoculum), the mean concentrations of dissolved organic carbon (DOC) were not significantly different from the initial mean DOC concentration measured on Day 0. Therefore, the test substance was not biodegradable under the test conditions within 28 days. The reference item sodium benzoate was completely biodegraded (100%) within seven days of exposure, thus confirming suitability of the activated sludge. In the toxicity control, containing the test item, the reference item sodium benzoate and activated sludge (inoculum), the initial DOC decreased by 55% within 13 days of exposure. Thus, according to the test guidelines, the test item was not inhibitory to activated sludge at the tested concentration of 82 mg/L because degradation was >35% within 14 days.

Description of key information

Key study: OECD 301-A and EU method C.4-A. GLP study.

The test substance was not biodegradable under the test conditions within 28 days.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

Key study: OECD 301-A and EU method C.4-A. GLP study.

In the test flasks, containing the test item and activated sludge (inoculum), the mean concentrations of dissolved organic carbon (DOC) were not significantly different from the initial mean DOC concentration measured on Day 0. Therefore, the test substance was not biodegradable under the test conditions within 28 days.