Sodium 6-amino-5-[[2-[(ethylphenylamino)sulphonyl]phenyl]azo]-4-hydroxynaphthalene-2-sulphonate

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

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

1981

GLP compliance:

not specified

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge (adaptation not specified)

Details on inoculum:

- Source of inoculum: mixed population of activated sewage sludge microorganisms from the aeration stage of Severn Trent Water PLC Sewage.
- Preparation of inoculum for exposure: the activated sludge was washed by repeatedly settling and resuspending with the test water.
- Concentration of sludge: equivalent to 750 mg dry weight/l.

Duration of test (contact time):

28 d

Initial conc.:

268 mg/L

Based on:

test mat.

Remarks:

equivalent to 100 ppm of C

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Agitation: by magnetic stirrers and compressed air via narrow bore glass tubes.
- Test temperature: 24 °C
- pH: pH values did not drop below 5.2 in any culture vessel during the course of the study and were adjusted to pH 7.3 daily.
- Dissolved oxygen: levels remained at approximately 5.7 mg O2/l or above in all cultures at all times.
- Continuous darkness: test was conducted in darkness.

SAMPLING
- Pevention of evaporation: losses by evaporation were made good by the addition of de-ionised water immediately prior to sampling.
- Volume: 20 ml samples were withdrawn from each vessel.
- Sample preparation: samples were filtered through 0.45 µm disposable filters, the first 5 ml was discarded .

Reference substance:

diethylene glycol

Parameter:

% degradation (DOC removal)

Value:

7

Sampling time:

28 d

Details on results:

Test item attained 7 % degradation after 28 days and therefore cannot be considered as inherently biodegradable.
The standard material, Digol, attained 100 % degradation after 28 days, thereby confirming the suitability of the inoculum and culture conditions.

Day	DOC value mg/l (mean of 3 replicate)		% of degradation
	Test item	Reference substance	Test item	Reference substance
0 hr	111.17	89.37	-	-
3 hrs	107.61	91.04	3	<2>
1	111.78	91.54	<1>**	<2>
2	113.22	63.96	<2>	28
3	112.29	40.98	<1>	54
6	100.98	13.93	9	84
8	112.96	6.28	<2>	93
10	102.01	0.00	8	100
14	119.8	0.00	<8>	100
16	115.61	0.00	<4>	100
21	96.65	0.00	13	100
23	107.52	0.00	3	100
27	102.25	0.00	8	100
28	103.62	0.00	7	100

<increase>

** The increase in % biodegradation is considered to be due to sampling/analytical variation.

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

Degradation (28d): 7 % based on DOC removal

Executive summary:

The inherently biodegradability potential of the test substance was assayed in Modified Zahn-Wellens Test, according to the OECD guideline 302B.

Test organisms were a mixed population of activated sewage sludge. Diethylene glycol was used as reference substance.

Test item attained 7 % degradation after 28 days and therefore cannot be considered as inherently biodegradable.

The standard material, Digol, attained 100 % degradation after 28 days, thereby confirming the suitability of the inoculum and culture conditions.

pH values did not drop below 5.2 in any culture vessel during the course of the study and were adjusted to pH 7.3 daily. Dissolved oxygen levels remained at approximately 5.7 mg O2/l or above in all cultures at all times.

Conclusion

Degradation (28d): 7 % based on DOC removal

Description of key information

Neither readily nor inherently biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The inherently biodegradability potential of the test substance was assayed in Modified Zahn-Wellens Test, according to the OECD guideline 302B. Under test conditions, test item attained 7 % degradation after 28 days and thus cannot be considered as inherently biodegradable. The standard material, Digol, attained 100 % degradation after 28 days, thereby confirming the suitability of the inoculum and culture conditions.

Acid Red 057 is an azo dye, which is not expected to be ready biodegradable because of its chemical structure and its specific function. Commonly, dyes undergo a primary transformation, i.e. discolouration due to the interruption of conjugation. However, the degradation process involves more steps and takes more time.