Registration Dossier

Environmental fate & pathways

Biodegradation in water: screening tests

Currently viewing:

Administrative data

Link to relevant study record(s)

Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2017-05-15 to 2017-05-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 301 A (Ready Biodegradability: DOC Die Away Test)
Version / remarks:
1992
Qualifier:
according to
Guideline:
EU Method C.4-A (Determination of the "Ready" Biodegradability - Dissolved Organic Carbon (DOC) Die-Away Test)
Qualifier:
according to
Guideline:
EPA OPPTS 835.3110 (Ready Biodegradability)
Version / remarks:
1998
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Details on inoculum:
- Source of activated sludge: aerobic activated sewage sludge from the aeration stage of the local wastewater treatment plant, ARA Birs (Birsfelden / Switzerland), which treats predominantly domestic sewage
- Storage conditions: 1 day aerated at room temperature
- Preperation: The aerobic activated sewage sludge was washed three times by centrifugation, decantation of the supernatant liquid phase and resuspension of the solid material in tap water and finally in mineral medium. Aliquots of the homogenized final sludge suspension were weighed, thereafter dried and the dry weight of the suspended solids was determined.
- Pretreatment: no
- Concentration of sludge: 4 g dry material per liter
- Final concentration in mineral medium: 30 mg dry material per liter
Duration of test (contact time):
12 d
Initial conc.:
38 mg/L
Based on:
DOC
Parameter followed for biodegradation estimation:
DOC removal
Details on study design:
TEST CONDITIONS
- Composition of medium: mineral medium according to testing guidelines
- Additional substrate: no
- Test temperature: 20 - 22 °C
- pH: 7.3 - 7.4
- pH adjusted: no
- Continuous darkness: no, diffuse light

TEST SYSTEM
- Culturing apparatus: 2000-mL Erlenmeyer glass vessels, cleaned with alcoholic hydrochloric acid, rinsed with ultrapure water and dried
- Number of culture flasks/concentration: 3
- Measuring equipment: DOC analyses were performed with the above filtrates in triplicate per sample using a TOC infrared gas analyzer equipped with an automatic sampler (Elementar Analysensysteme GmbH, Langenselbold, Germany).
- Test performed in open system: no, loosely covered with an aluminum cap to reduce losses by evaporation

SAMPLING
- Sampling frequency: on exposure day 0, 2, 5, 7, 9 and 12
- Sampling method: one sample of 10-12 mL was taken
- Sample preparation: filtered through a 0.45-μm filter. The first 2-3 mL of the filtrate were discarded

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes, 3 replicates
- Procedure control: yes, 3 replicates
- Toxicity control: yes, 1 replicate
Reference substance:
benzoic acid, sodium salt
Preliminary study:
Prior to test start, the solubility of the test item in mineral medium was checked, and the test item was found to be soluble at a concentration of 100 mg/L. The measured dissolved organic carbon content (DOC) of this solution was 0.764 mg C/mg test item. The measured total organic carbon content (TOC) was 0.771 mg C/mg test item.
Key result
Parameter:
% degradation (DOC removal)
Value:
98
Sampling time:
12 d
Details on results:
In the test vessels containing the test item in inoculated mineral medium the mean concentration of dissolved organic carbon (DOC) continuously decreased from initially 28.8 mg/L on Day 0 to 0.6 mg/L on Day 12, at the end of the test. Expressed as percentage DOC removal, this represents a mean biodegradation value of 98 %. The mean biodegradation of the test item was 79 % on Day 5. Therefore, the pass level for ready biodegradability, i.e. at least 70 % removal of DOC in a 10 day window within the 28 day period of the test, was reached.
In the procedure controls, average biodegradation of the reference item sodium benzoate was 99 % by Exposure Day 12, i.e. at the end of the test, thus confirming suitability of the activated sludge (≥ 60 % degradation by Exposure Day 14).
In the toxicity control, containing both Methyl Benzyl Alcohol (corresponding to 49.5 % of total DOC) and the reference item sodium benzoate (corresponding to 50.5 % of total DOC) in inoculated mineral medium, the initial DOC concentration of 59.4 mg/L measured on Day 0 decreased to 10.7 mg/L on Day 12. Biodegradation amounted to 82 % on Exposure Day 12, i.e. at the end of the test. Thus, according to the test guidelines, the test item Methyl Benzyl Alcohol was not inhibitory to activated sludge at the tested concentration of 38 mg/L because degradation was >35% within 14 days.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
The test item was found to be readily biodegradable and degraded completely after 12 days of exposure to activated sludge under the conditions of the conducted DOC Die-Away Test (OECD 301 A).
Executive summary:

The test item was investigated for its ready biodegradability in a 28-Day DOC Die-Away Test according to the OECD Guideline for Testing of Chemicals, No. 301 A (1992). In accordance with the test guidelines the test was ended after 12 days since the biodegradation curve of the test item had reached a plateau over at least three determinations and was biodegraded completely. Expressed as percentage DOC removal, this represents a mean biodegradation value of 98 %. The pass level for ready biodegradability, i.e. at least 70 % removal of DOC in a 10-day window within the 28-day period of the test, was reached. In conclusion, the test item was found to be readily biodegradable under the test conditions within 12 days. In the toxicity control, containing both test item and the reference item sodium benzoate, the initial DOC decreased by 82 % within 12 days of exposure. Thus, the test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 38 mg/L.

Description of key information

The test item was found to be readily biodegradable and degraded completely after 12 days of exposure to activated sludge under the conditions of the conducted DOC Die-Away Test (OECD 301 A).

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

The test item was investigated for its ready biodegradability in a 28-Day DOC Die-Away Test according to the OECD Guideline for Testing of Chemicals, No. 301 A (1992). In accordance with the test guidelines the test was ended after 12 days since the biodegradation curve of the test item had reached a plateau over at least three determinations and was biodegraded completely. Expressed as percentage DOC removal, this represents a mean biodegradation value of 98 %. The pass level for ready biodegradability, i.e. at least 70 % removal of DOC in a 10-day window within the 28-day period of the test, was reached. In conclusion, the test item was found to be readily biodegradable under the test conditions within 12 days. In the toxicity control, containing both test item and the reference item sodium benzoate, the initial DOC decreased by 82 % within 12 days of exposure. Thus, the test item had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 38 mg/L.