2-[[4-[ethyl(2-hydroxyethyl)amino]phenyl]azo]-6-methoxy-3-methylbenzothiazolium methyl sulphate

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

For justification of read-across please refer to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration of test (contact time):

6 h

Key result

Remarks on result:

not determinable because of methodological limitations

Remarks:

Only parent substance was analysed. No information is available on potential metabolites. No conclusion can be made whether the test substance was subject to ultimate biodegradation.

Transformation products:

not measured

Details on transformation products:

No analysis were conducted to indentify potential transformation products.

Evaporation of parent compound:

no

Remarks:

Due to the low vapour pressure of the substance (see IUCLID section 4.6) significant evaporation of the parent substance is not expected.

Volatile metabolites:

not measured

Residues:

yes

Remarks:

Parent substance was analysed in influent, effluent, sludge and liquid phase of activated sludge units. No information on potential metabolites available.

Details on results:

RESULTS OF SUPPLEMENTARY EXPERIMENTS:
- Only slight (but non-significant) reduction of the dehydrogenase activity at the end of the test.
- No inhibition of nitrification.
- No degradation observed in subsequent OECD 302 C (MITI II Test), neither with non-adapted nor adapted sludge from Husmann units.

Test substance analysis in the Husmann units:

Unit 1	Influent [µg test substance per time period]	Cumulative values [µg test substance per time period]				Balance [%] (Sludge, total in relation to influent)
Time period		Influent, total	Sludge	Effluent	Sludge, total (= Sludge + Effluent)
26.10. – 28.10.1992	911	911	994	30	1024	112.40
28.10. – 30.10.1992	917	1828	1675	53	1728	94.53
30.10. – 02.11.1992	1740	3568	2622	99	2721	76.26
02.11. – 03.11.1992	629	4197	3446	116	3562	84.87
03.11. – 04.11.1992	839	5036	3276	143	3419	67.89
04.11. – 06.11.1992	1342	6378	3380	199	3579	56.11
06.11. – 09.11.1992	1908	8286	4186	318	4504	54.36
09.11. – 11.11.1992	1064	9350	4194	431	4625	49.47
11.11. – 13.11.1992	1187	10537	4194	446	4640	44.04
13.11. – 16.11.1992	1423	11960	4598	563	5161	43.15
16.11. – 18.11.1992	1338	13298	4208	644	4852	36.49
18.11. – 20.11.1992	1149	14447	3586	706	4292	29.71
20.11. – 23.11.1992	1600	16047	2980	776	3756	23.41
23.11. – 25.11.1992	1294	17341	2374	824	3198	18.44
25.11. – 27.11.1992	1264	18605	2160	847	3007	16.16

Unit 2	Influent [µg test substance per time period]	Cumulative values [µg test substance per time period]				Balance [%] (Sludge, total in relation to influent)
Time period		Influent, total	Sludge	Effluent	Sludge, total (= Sludge + Effluent)
26.10. – 28.10.1992	918	918	1052	15	1024	111.55
28.10. – 30.10.1992	917	1835	1838	69	1907	103.92
30.10. – 02.11.1992	1730	3565	2622	171	2793	78.35
02.11. – 03.11.1992	641	4206	3088	209	3297	78.39
03.11. – 04.11.1992	856	5062	3215	264	3479	68.73
04.11. – 06.11.1992	1342	6404	2935	352	3287	51.33
06.11. – 09.11.1992	1901	8305	2733	418	3151	37.94
09.11. – 11.11.1992	1103	9408	2737	514	3251	34.56
11.11. – 13.11.1992	1230	10638	2781	562	3343	31.43
13.11. – 16.11.1992	1467	12105	3129	718	3847	31.78
16.11. – 18.11.1992	1350	13455	3117	767	3884	28.87
18.11. – 20.11.1992	1172	14627	3119	809	3928	26.85
20.11. – 23.11.1992	1659	16286	2919	941	3860	23.70
23.11. – 25.11.1992	1294	17580	2727	1021	3748	21.32
25.11. – 27.11.1992	1322	18902	2331	1077	3408	18.03

 

Degradation of the organic medium:

Unit 1				Unit 2
Date	Influent mg/L TOC	Effluent mg/L TOC	% Elimination	Date	Influent mg/L TOC	Effluent mg/L TOC	% Elimination
20.10.92	68.5	8.67	87.34	20.10.92	94.4	8.25	87.19
21.10.92	69.7	12.47	82.11	21.10.92	64.5	11.51	82.16
22.10.92	69.7	8.83	87.33	22.10.92	64.5	10.08	84.37
23.10.92	68.4	10.96	83.98	23.10.92	64.5	9.58	85.15
26.10.92	67	6.81	89.84	26.10.92	64.2	6.67	89.61
28.10.92	64.9	4.16	93.59	28.10.92	61.7	4.19	93.21
30.10.92	71	2.74	96.14	30.10.92	69.4	2.70	96.11
02.11.92	63.4	2.63	95.85	02.11.92	68.3	2.74	95.99
04.11.92	72.4	4.11	94.32	04.11.92	72.7	3.91	94.62
06.11.92	68.4	4.52	93.39	06.11.92	69.6	5.03	92.77
09.11.92	72.3	7.55	89.56	09.11.92	69.6	10.39	85.07
11.11.92	70.9	2.08	97.07	11.11.92	68.4	2.37	96.54
13.11.92	69.4	2.50	96.40	13.11.92	66.8	3.66	94.52
16.11.92	73.5	3.13	95.74	16.11.92	72.2	3.46	95.21
18.11.92	67.1	2.84	95.77	18.11.92	68.5	3.44	94.98
20.11.92	66.9	2.95	95.59	20.11.92	64.1	3.45	94.62
23.11.92	67.7	3.48	94.86	23.11.92	66.8	3.89	94.18
25.11.92	69.4	3.57	94.86	25.11.92	67.2	3.31	95.07
Mean elimination:			92.43	Mean elimination:			91.74

 

Validity criteria fulfilled:

yes

Conclusions:

A conclusion on the ulitmate biodegradation of the test substance cannot be made.

Executive summary:

The degradation of the test substance was investigated in a experiment that was conducted in accordance with OECD Guideline 303 A (Activated Sludge Units). The test was conducted in duplicate using Husmann units (mean retention time: 6 h). The TOC concentration of the organic medium was 60 -70 mg/L, the mean test substance concentration in the influent was 77 µg/L, which was stated to be similar to real-life conditions (-> STP influent concentration at production sites). The total test duration was 31 days.

Despite of continuous addition of the test substance to the activated sludge units and high initial adsorption of the test substance to sewage sludge, the test substance did not accumulate in the test system (-> sewage sludge). At the end of the test only < 20 % of the total amount of test substance applied in the test was adsorbed to sludge, < 6 % of the total test substance amount of the influent could be found in the effluent. Analysis results of test substance adsorbed to sludge would indicate biodegradation of the test substance. Complete degradation of the test substance could however not be demonstrated to due methodological limitations (only parent substance was analysed, degradation products were not analysed).

In the subsequent degradation test that was conducted according to OECD 302 C (MITI II Test) with non-adapted and adapted sewage sludge from the Husmann units, the test substance did not degrade (0 % after 20 days).

This information is used in a read-across approach in the assessment of the substance to be registered.

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reference 2

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Duration of test (contact time):

d

Key result

% Degr.:

0

Parameter:

TOC removal

Sampling time:

31 d

Validity criteria fulfilled:

not specified

Conclusions:

No elimination was observed after 31 days under the conditions of OECD 303 A.

Executive summary:

The biodegradation of the test item was investigated under the conditions of OECD Test Guideline 303 A (Simulation Test - Aerobic Sewage Treatment: Activated Sludge Units). The TOC concentration of the organic medium was ca. 100 mg/L, the applied test substance concentration was 20 mg/L.

The elimination of the test substance after 31 days was reported to be 0 %.

This information is used in a read-across approach in the assessment of the substance to be registered.

For justification of read-across please refer to the read-across report attached to IUCLID section 13.

Description of key information

The elimination of the test substance was investigated in two separate experiments which were conducted in accordance with OECD Guideline 303 A (Activated Sludge Units).

 

The first test was conducted 1989 over a total test duration of 31 days (Stutz, 1990). Elimination was followed by determination of the TOC concentration of the effluent. The TOC concentration of the organic medium applied in the test was 100 mg/L, while the TOC concentration of the test substance was 20 mg/L. No elimination could be observed in this study.

This is however surprising, as the test substance is a cationic compound which is expected to highly adsorb to sludge particles.

The documentation of this study is very poor and is not sufficient for the assessment of the study results. Therefore, it is considered not reliable and is not further considered in the assessment.

 

The second study was conducted 1992 over a period of 31 days using duplicate Husmann units (Schnalke et al., 1993). The TOC concentration of the organic medium was 60 -70 mg/L. The mean test substance concentration applied in the influent was rather low (77 µg/L, but still in line with OECD 303 A) and similar to real-life conditions. At the beginning of the test, a high initial adsorption of the test substance to sewage sludge could be observed. Although test substance was continuously added to the test vessels, the test substance did not accumulate in the sludge: only < 20 % of the total amount of test substance applied in the test was adsorbed to sludge at the end of the test. Less than 6 % of the total test substance amount of the influent could be detected in the effluent.

In the subsequent degradation test that Schnalke et al. (1993) conducted according to OECD 302 C (MITI II Test) with non-adapted and adapted sewage sludge from the Husmann units, the test substance did not degrade (0 % after 20 days).

Biodegradation in Continuous Activated Sludge tests can only directly be determined when the test material is non-sorptive. As only the parent substance was analysed and degradation products were not considered, complete degradation of the test substance could not be demonstrated. Furthermore, the OECD 303 A test does in general not provide a definitive degradation half-life that can be compared directly to the persistence criteria as defined in REACH Annex XIII.

However, the results from the OECD 303 A test may be used to estimate the removal of the test substance in sewage treatment plants (STP), the resulting effluent concentration, and the concentration in the receiving aquatic environment.

Additional information

This information is used in a read-across approach in the assessment of the substance to be registered.

For justification of read-across please refer to the read-across report attached to IUCLID section 13.