Disodium 4,4'-methylenebis[3-hydroxy-2-naphthoate]

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

Study period:

10 JUN 2013 - 29 AUG 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

17 July 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim (20 October 2010)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Municipal sewage treatment plant, 31137 Hildesheim, Germany
- Storage conditions: After sedimentation the supernatant was decanted and maintained in an aerobic condition by aeration with CO2-free air.
- Storage length: 2 days
- Preparation of inoculum for exposure: The test medium, consisting of the required volumes of mineral medium stock solutions, ultrapure water and 10 mL/L inoculum, were prepared in a measuring flask. 250 mL of this solution were filled in the brown glass bottles of the inoculum control, using a 250 mL measuring flask.
- Pretreatment: The activated sludge was washed twice with chlorine free tap water. After the second washing the settled sludge was filled up with mineral salts medium and was maintained in an aerobic condition by aeration for 2 hours. Thereafter the sludge was homogenized with a blender.
- Concentration of sludge: 10 ml/L
- Initial cell/biomass concentration: Colony forming units (CFU) of the inoculum were determined prior to test start by standard dilution plate count: 7.7 x 10E8 CFU/L. The CFU concentration of the inoculum corresponds to approx. 0.77 x 10E7 CFU/L in the final test solution.

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: Mineral salts medium according to OECD 301 F
- Test temperature: 19.5 - 20°C
- pH: 7.84 (start), 7.80 and 7.75 (end)
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: brown glass bottles (volume 500 mL); test volume 250 mL
- Number of culture flasks/concentration: 2
- Method used to create aerobic conditions: Continuous stirring
- Measuring equipment: The bottles were closed with OxiTop® measuring heads and the measuring system was activated.
- Details of trap for CO2 and volatile organics if used: A rubber sleeve with soda lime was hung into the opening of the bottles to absorb evolved CO2.

SAMPLING
- Sampling frequency: every 112 min
- Sampling method: OxiTop® measuring system

CONTROL AND BLANK SYSTEM
- Inoculum blank: Test medium without test and / or reference item (2 replicates)
- Toxicity control: For the toxicity control, the test and reference item were weighed out and directly transferred into the test vessel with 250 mL test medium (1 replicate).
- Other: For the functional control the reference item sodium benzoate was weighed out and directly transferred into the test vessel with 250 mL test medium (1 replicates).

Reference substance:

benzoic acid, sodium salt

Preliminary study:

The biodegradation in % was calculated based on the ThOD of 1. 78 mg O2/mg test item.

Test performance:

The pass level for ready biodegradation (> 60 % degradation) was reached within 3 days.

The validity criterion that the degradation should be > 60 % after 14 d was fulfilled.

Stages of Biodegradation:
The adaptation phase changed to degradation phase within 2 days (degradation > 10 %) and the biodegradation came to a maximum of 100 % on day 13.

Parameter:

% degradation (O2 consumption)

Value:

12

Sampling time:

28 d

Details on results:

The mean biodgradation of both test item replicates reached the 10 % level (beginning of biodegradation) within 27 days. The 60 % pass level was not reached within 28 days by both test item replicates. After 28 days the mean biodegradation was 12 %. The degradation of the test item did not reach 60 % within the 10-day window and after 28 days of incubation. Therefore, the test item is not considered to be readily biodegradable.


Biodegradation [%]

Day Functional Control (Reference item) Test Item (R1) Test Item (R2) Toxicity control (Test Item + Reference item)
1 8 0 0 0
7 95 0 0 48
14 100 0 6 51
21 100 1 14 55
28 100 2 21 58

Results with reference substance:

Results of the toxicity control
In the toxicity control the biodegradation achieved 51 % after 14 days. After 28 days the biodegradation came to 58 %. The validity criterion that the test item should not inhibit the biodegradation of the reference item was fulfilled.

Results of functional control
In order to check the activity of the test system sodium benzoate was used as functional control. The pass level > 60 % was reached within 3 days. The biodegradation reached a maximum of 100 % degradation on day 13.

Please refer to 'Details on results'

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The degradation rate of the test material did not reach 60 % within the 10-day window and after 28 days of incubation. Thus, the test item is not readily biodegradable.

Executive summary:

Purpose

The test item was investigated for its ready biodegradability in a Manometric Respirometry Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.The GLP study was performed according to OECD TG 301F.

Result

Biodegradation of test item

After correction of the mean biochemical oxygen demand of the inoculum controls at the end of the 28-day exposure period the degradation of 12 % was found.

Biodegradation of sodium benzoate

The reference item was sufficiently degraded to 100 % after 14 days of incubation, thus confirming the suitability of the used activated sludge inoculum.

Biodegradation in the Toxicity Control

In the toxicity control containing both, the test item and the reference item, 51 % biodegradation was noted within 14 days and 58 % biodegradation was determined after 28 days of incubation. Thus, the test item can be assumed to be not inhibitory on the activated sludge microorganisms.

Conclusion

The degradation rate of the test material did not reach 60 % within the 10-day window and after 28 days of incubation. Thus, the test item is not readily biodegradable.

Description of key information

Key, 28 d, OECD 301F, GLP: not ready biodegradable

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

Purpose

The test item was investigated for its ready biodegradability in a Manometric Respirometry Test over a period of 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control.The GLP study was performed according to OECD TG 301F.

Result

Biodegradation of test item

After correction of the mean biochemical oxygen demand of the inoculum controls at the end of the 28-day exposure period the degradation of 12 % was found.

Biodegradation of sodium benzoate

The reference item was sufficiently degraded to 100 % after 14 days of incubation, thus confirming the suitability of the used activated sludge inoculum.

Biodegradation in the Toxicity Control

In the toxicity control containing both, the test item and the reference item, 51 % biodegradation was noted within 14 days and 58 % biodegradation was determined after 28 days of incubation. Thus, the test item can be assumed to be not inhibitory on the activated sludge microorganisms.

Conclusion

The degradation rate of the test material did not reach 60 % within the 10-day window and after 28 days of incubation. Thus, the test item is not readily biodegradable.