Disodium 2-(11-oxido-3-oxo-3H-dibenzo[c,h]xanthen-7-yl)benzoate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-02-16 to 2010-03-24

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test)

Version / remarks:

1992-07-17

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.9 (Biodegradation: Zahn-Wellens Test)

Version / remarks:

2008-05-30

Deviations:

no

GLP compliance:

not specified

Remarks:

The study was conducted in accordance with ISO/IEC 17025

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature, protected from light.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge: Activated sludge from the aeration tank of the ARA Werdholzli (CH-8048 Zurich), a municipal biological waste water treatment plant, not adapted, not pre-conditioned. Sampling: 16 February 2010; 10.00 a.m.
- Method of cultivation: The activated sludge was used after sampling from the treatment plant without adaptation. However, the sludge was pre-conditioned for 1-4 days (aerated but not fed).
- Preparation of inoculum for exposure: Prior to the test the sludge was washed twice with tap water.
- Concentration of sludge: 0.2 g/L
- Water filtered: no

Duration of test (contact time):

28 d

Initial conc.:

1 282 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: See "Any other information on Materials and Methods"
- Additional substrate: No
- Test temperature: 22 ± 2 °C
- pH: 7.4 ± 0.2
- pH adjusted: Yes, with HCl
- Aeration of dilution water: The test vessels were stirred (100 rpm) and aerated with synthetic CO2-free air for a maximum test period of 28 days.
- Suspended solids concentration: 0.2 g/L
- Continuous darkness: Yes

TEST SYSTEM
- Culturing apparatus: 1200 mL closed glass bottle containing a total volume of test solution of 800 mL
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: synthetic CO2-free air
- Measuring equipment: TOC-Analyzer (Shimadzu Schweiz GmbH, Römerstr. 3, 4153 Reinach, Switzerland)
- Details of trap for CO2 and volatile organics if used: gas-absorption bottles containing 125 mL of 0.13 M KOH

SAMPLING
- Sampling frequency: on day 0, 0.125, 1, 3,8, 10, 14, 17, 21, 24, 27, 28
- Sampling method: samples taken from the gas-absorption bottles.

CONTROL AND BLANK SYSTEM
- Inoculum blank: Yes
- Abiotic sterile control: No
- Toxicity control: Yes

STATISTICAL METHODS:
No statistical analysis was performed.

Reference substance:

diethylene glycol

Remarks:

50.0 mg/L (DOC)

Key result

Parameter:

% degradation (DOC removal)

Value:

15

Sampling time:

28 d

Results with reference substance:

The positive control, diethyleneglycol, showed 99 % biodegradation after 14 days of incubation thus confirming suitability of inoculum and test conditions.

Validity criteria fulfilled:

yes

Interpretation of results:

not inherently biodegradable

Conclusions:

In a screening test for aerobic biodegradability in water according to OECD Guideline 302 B, an aqueuos formulation, containing 6.3 % of the test item, was not inherently biodegradable.

Executive summary:

The inherent biodegradability an aqueous formulation containing 6.3 % test item exposed to activated non-adapted sludge of a municipal sewage treatment plant was investigated under aerobic static conditions according to OECD Guideline 302 B (Zahn-Wellens/EMPA test). Based on the data of the individual DOC determinations the test item reached a biodegradation of 15 % after 28 days. No significant biodegradation of the test item was observed. No significant elimination of the test item due to adsorption to the activated sludge, on the glass surface or other physico-chemical processes was found as determined by means of DOC measurements 3 h after the start of the test. The positive control, diethyleneglycol, showed 99 % biodegradation after 14 days of incubation thus confirming suitability of inoculum and test conditions. The test was considered valid, since the degradation of the reference compound reached more than 70 % within 14 days of incubation. The biodegradation of the test item is based on CO2 evolution and calculated as % ThCO2 reached -20 % after 28 days of incubation, indicating some toxic effects to the activated sludge microorganisms. The extent of mineralization of the procedure control with diethyleneglycol was 90 % based on ThCO2. Based on these results the formulation is not inherently biodegradable under the conditions of the OECD guideline No 302, since less than 20 % degradation was attained after 28 days of contact time.

Consequently, the test item can be considered to be neither readily nor inherently biodegradable.

Description of key information

In a test for aerobic biodegradability in water according to OECD Guideline 302 B, the test item was not inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

To determine the inherent biodegradability of the test item, an aqueous formulation containing 6.3 % test item was exposed to activated non-adapted sludge of a municipal sewage treatment plant under aerobic static conditions according to OECD Guideline 302 B (Zahn-Wellens/EMPA test). Based on the data of the individual DOC determinations the test item reached a biodegradation of 15 % after 28 days. No significant biodegradation of the test item was observed. No significant elimination of the test item due to adsorption to the activated sludge, on the glass surface or other physico-chemical processes was found as determined by means of DOC measurements 3 h after the start of the test. The positive control, diethyleneglycol, showed 99 % biodegradation after 14 days of incubation thus confirming suitability of inoculum and test conditions. The test was considered valid, since the degradation of the reference compound reached more than 70 % within 14 days of incubation. The biodegradation of the test item, based on CO2 evolution and calculated as % ThCO2 reached -20 % after 28 days of incubation, indicating some toxic effects to the activated sludge microorganisms. The extent of mineralization of the procedure control with diethyleneglycol was 90 % based on ThCO2. Based on these results the test item is not inherently biodegradable under the conditions of the OECD guideline No 302, since less than 20 % degradation was attained after 28 days of contact time.

Since the aqueous formulation is not inherently biodegradable, it can be concluded, that the test item is neither readily nor inherently biodegradable.