Reaction mass of trisodium [m[7-[[4'-[[6-benzamido-1-hydroxy-3-sulpho-2-naphthyl]azo]-3,3'-dihydroxy[1,1'-biphenyl]-4-yl]azo]-8-hydroxynaphthalene-1,6-disulphonato(7-)]]dicuprate(3-) and trisodium [m[4-[[4'-[[6-benzamido-1-hydroxy-3-sulpho-2-naphthyl]azo]-3,3'-dihydroxy[1,1'-biphenyl]-4-yl]azo]-3-hydroxynaphthalene-2,7-disulphonato(7-)]]dicuprate(3-)

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:

From October 10th to November 07th, 1985

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

September 1982

GLP compliance:

yes

Specific details on test material used for the study:

The test solutions were prepared by adding the test material directly in the test water.

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source: ARA Rhein, Pratteln, Switzerland.
- Pretreatment: the sludge was centrifuged and washed three times with drinking water.
- Preparation of inoculum for exposure: the sludge was suspended in water with a solids content of 4 g/l and - after the addition of 20 ml synthetic sewage per litre sludge suspension - aerated overnight at 20 °C.

Duration of test (contact time):

28 d

Initial conc.:

180 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Test vessels: 4 litres glass beaker with 2 litre test solution.
- Aeration: air flow 0.5 to 1 l/min.
- Light: diffuse light.
- Sludge: 1 g/l
- Temperature: 22 ± 3 °C

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: drinking water.
- Total hardness: about 180 mg CaCO3/l.
- pH: 7.6 to 8.0.

Reference substance:

benzoic acid, sodium salt

Remarks:

725 mg/l, corresponding to 415 mg DOC/l

Parameter:

% degradation (DOC removal)

Value:

57

Sampling time:

3 h

Parameter:

% degradation (DOC removal)

Value:

86

Sampling time:

28 d

Results with reference substance:

DOC elimination > 90 % after 5 days.

DOC-elimination

Sampling time	Test material mg DOC/l*	Control mg DOC/l*	DOC net mg/l	DOC elimination (%)
3 hours	180	9	171	57
5 days	67.5	6.5	61	84.5
6 days	63	9.5	53.5	86.5
8 days	64	5	59	85
12 days	64.5	6.5	58	85.5
13 days	61.5	6	55.5	86
15 days	66	5	61	84.5
18 days	62	3	59	85
20 days	64	5.5	58.5	85.5
22 days	65	5.5	59.5	85
25 days	57.5	2	55.5	86
27 days	54.5	2	52.5	87
28 days	58	4.5	53.5	86.5

*mean values of duplicate determination

Interpretation of results:

other: most of the test item resulted to be efficiently removed after 5 days

Conclusions:

Based on these results, most of the test item resulted to be efficiently removed after 5 days.

Executive summary:

The biodegradability potential of test item exposed to activated sludge, domestic, non-adapted, was investigated under aerobic static conditions. The procedures outlined into the OECD guideline 302 B were followed.

Based on the data of the individual DOC determinations the test item reached a bioelimination of 86 % alter 5 days. The main elimination process occurred during the first days; in the first 3 hours the 57 % of the initial DOC resulted to be removed. Maximum elimination was attained after 5 days of incubation. Some elimination of the test substance 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, sodium benzoate, showed a biodegradation percentage higher than 90 after 5 days of incubation, confirming suitability of inoculum and test conditions.

Conclusion

Based on these results, most of the test item resulted to be efficiently removed after 5 days.

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 biodegradability potential of test item exposed to activated sludge, domestic, non-adapted, was investigated under aerobic static conditions. The procedures outlined into the OECD guideline 302 B were followed. Based on the data of the individual DOC determinations the test item reached a bioelimination of 86 % alter 5 days. The main elimination process occurred during the first days; in the first 3 hours the 57 % of the initial DOC resulted to be removed.

On the basis of the substance removal and on the basis the physicochemical properties of the substance, it is expected that most of the elimination of the test substance should be attributed to adsorption to the activated sludge, on the glass surface or other physico-chemical processes. Based on these results, most of the test item resulted to be efficiently removed after 5 days. However, it is probable that the test item was mainly removed by adsorption and not degraded.

The expectation is confirmed by the comparison with the results obtained into a MITI test conducted on the structural analogous Similar Substance 01; the read acorss approach can be considered as reliable and adequate to investigate the biodegradability potential of the test item. Details on the read across approach are given into the IUCLID section 13.

Similar Substance 01 was investigated for its inherent biodegradability in a manometric respirometry test, over 28 days. The oxygen consumption of the test item in the test media was in the normal range of the oxygen consumption in the inoculum controls. Consequently, the substance resulted to be not biodegradable under the conditions of the test within 28 days. No degradation of the test item occurred in the abiotic control under the conditions of the test.

In the toxicity control, containing both test item and the reference item sodium benzoate, no inhibitory effect on the biodegradation of the reference item was determined. Thus, had no inhibitory effect on the activity of activated sludge microorganisms at the tested concentration of 65 mg/l. In the procedure controls, the reference item (sodium benzoate) was degraded by an average of 73 % and 84 % by exposure days 7 and 14, respectively, thus confirming the suitability of the activated sludge.

In conclusion, Direct Blue 251 is expected to be neither readily nor inherently biodegradable.