[No public or meaningful name is available]

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 September 26 to October 28, 2005

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Qualifier:

according to guideline

Guideline:

OECD Guideline 302 C (Inherent Biodegradability: Modified MITI Test (II))

Version / remarks:

1981

Deviations:

yes

Remarks:

not impacting the study outcomes (detail below)

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

No emulsifiers or solvents were used but ultrasound dispersion was employed for 15 minutes to obtain a homogenous suspension of the test item.

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic (adaptation not specified)

Details on inoculum:

- Source of activated sludge: ARA Ergolz II, Füllinsdorf, Switzerland.
- Pre-treatment: the sludge was washed twice with tap water by centrifugation and the supernatant liquid phase was decanted. A homogenized aliquot of the final sludge suspension was weighed, thereafter dried and the ratio of wet to dry weight was calculated.
- Initial cell/biomass concentration: 4 g dry material per liter.
- Storage: during holding, the sludge was aerated at room temperature until use.
- Preparation of inoculum for exposure: prior to use, the sludge was diluted with test water to a concentration of about 1 g dry material per liter. Based on the determined dry weight of this diluted activated sludge defined amounts were added to test water to obtain a final concentration of 100 mg dry material per liter.

Duration of test (contact time):

28 d

Initial conc.:

65 mg/L

Based on:

test mat.

Initial conc.:

63 - 64 mg/L

Based on:

COD

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test water: the test water was prepared according to the OECD guideline 301 F, 1992. Analytical grade salts were dissolved in purified water.
- Vessels: 500-ml Erlenmeyer flasks.
- Stirring: continuous stirring.
- Test temperature: 22 °C, maintained with a built-in thermostat and checked once per week.
- pH: the pH measured in all flasks at the start of the test was 7.4. At the end of exposure (day 28) pH values of 7.3 - 7.7 were measured.
- pH adjusted: the pH of test water was adjusted from 7.7 to 7.4 with a diluted hydrochloric acid solution.
- Continuous darkness: yes; darkness.

CONTROL AND BLANK SYSTEM
- Inoculum blank: two replicates.
- Abiotic sterile control: one replicate; poisoned with mercury dichloride at a concentration of 10 mg/l.
- Toxicity control: one replicate.

DETERMINATION OF THE CHEMICAL OXYGEN DEMAND
Due to the complex composition of the test item, its chemical oxygen demand (COD) was determined according to the EU Commission Directive 92/69/EEC, C.6 following DIN 38414-S9 and in compliance with ISO 17025.

MODIFICATION FROM OECD GUIDELINE
- Activated sludge from only one source was used.
- The test water according to OECD Guideline for Testing of Chemicals No. 301 F, Ready Biodegradability: Manometric Respirometry Test, 1992 was used.
- Only the biological oxygen demand (BOD) was monitored.

Reference substance:

benzoic acid, sodium salt

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

The percent biodegradation of the test item was calculated based on the chemical oxygen demand (COD) of 0.98 mg O2/mg test item.
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, was not biodegradable under the conditions of the test within 28 days.

ABIOTIC CONTROL
No degradation of the test item occurred in the abiotic control under the conditions of the test.

TOXICITY CONTROL
The percent biodegradation in the toxicity control containing both the test item and the reference item was calculated based on the COD of the test item and the ThOD of the reference item.
In the toxicity control, the course of biodegradation over the 28-day exposure period was similar to that in the two procedure controls containing the reference item, only. Within 14 days of exposure, biodegradation of 63 % was calculated.
Thus, the test item had no inhibitory effect on activated sludge microorganisms at the tested concentration of 65 mg/l.

Results with reference substance:

The percent biodegradation of the reference item sodium benzoate was calculated based on the theoretical oxygen demand of 1.67 mg O2/mg (ThOD).
In the procedure controls, the reference item was degraded by an average of 73 % and 84 % by exposure day 7 and 14, respectively, thus confirming suitability of the activated sludge. At the end of the test (Day 28), the reference item was degraded by an average of 89 %.

Biodegradation in the test flasks

Time (days)	Percentage biodegradation*
	Test item		Reference substance		Toxicity control
0	0	0	0	0	0
1	--	--	--	--	--
2	-7	-7	51	51	42
3	-11	-11	58	56	43
4	-13	-13	64	60	48
5	-17	-17	69	64	51
6	-18	-18	73	68	54
7	-20	-19	77	70	56
8	-20	-20	80	72	56
9	--	--	--	--	--
10	-23	-21	83	75	58
11	-24	-20	85	76	60
12	-22	-19	86	77	60
13	-24	-20	88	78	61
14	-24	-20	89	78	63
15	--	--	--	--	--
16	--	--	--	--	--
17	-25	-17	92	80	64
18	-27	-19	93	80	64
19	-26	-18	93	81	65
20	-28	-18	94	81	64
21	-27	-19	94	81	65
22	-28	-19	94	81	66
23	-29	-18	94	81	66
24	-29	-20	94	81	66
25	-30	-19	95	81	66
26	-29	-18	95	82	67
27	-30	-17	96	82	68
28	-30	-17	96	82	68
Mean (Day 28)	-24**		89

*Corrected for the mean oxygen uptake of the inoculum controls

** Negative value due to higher oxygen consumption in the inoculum controls than in the test flasks with test item.

-- Not determined

Oxygen consumption in the test flasks

Time (days)	Cumulative oxygen consumption (mg/l)
	Test item		Inoculum control		Reference substance		Abiotic control	Toxcity control
0	0	0	0	0	0	0	0	0
1	--	--	--	--	--	--	--	--
2	5	5	8	11	95	94	0	106
3	7	7	12	16	111	107	0	112
4	10	10	16	21	126	119	0	128
5	11	11	19	24	137	128	0	138
6	13	13	22	27	147	138	0	148
7	13	14	23	29	154	143	0	154
8	15	15	25	31	161	149	0	158
9	--	--	--	--	--	--	--	--
10	17	18	28	35	170	157	0	166
11	17	19	28	36	174	159	0	170
12	19	21	29	37	177	162	0	172
13	19	22	30	39	181	164	0	176
14	20	23	31	40	184	166	0	180
15	--	--	--	--	--	--	--	--
16	--	--	--	--	--	--	--	--
17	21	26	32	42	191	171	0	184
18	21	26	33	43	193	172	0	186
19	22	27	33	44	194	173	0	188
20	22	28	34	45	196	174	0	188
21	23	28	34	46	197	175	0	190
22	23	29	35	47	198	177	0	192
23	23	30	36	47	199	177	0	194
24	24	30	37	48	200	178	0	194
25	24	31	37	49	201	179	0	196
26	25	32	38	49	202	180	0	198
27	25	33	38	50	204	181	0	200
28	25	33	38	50	205	181	0	200

-- No reading taken

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The substance resulted to be not biodegradable under the conditions of the test.

Executive summary:

The test item was investigated for its inherent biodegradability in a manometric respirometry test over 28 days based on the OECD guideline 302 C (1981). The following modifications were made: activated sludge from one source was used; the test water composition was slightly changed; and only the biological oxygen demand (BOD) was monitored.

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.

Conclusion

Not inherently biodegradable.

Description of key information

Neither readily nor inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

The test item was investigated for its inherent biodegradability in a manometric respirometry test over 28 days based on the OECD guideline 302 C (1981).

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. 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 (Büche, 2005).

Additionally, an assessment of the ready biodegradability was performed which determined that the substance is not readily biodegradable based on its chemical structure and specific inherent function of a dye.