4-(4-isopropoxyphenylsulfonyl)phenol

Biodegradation in water and sediment: simulation tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: sediment simulation testing

Data waiving:

exposure considerations

Justification for data waiving:

the study does not need to be conducted because direct and indirect exposure of sediment is unlikely

Transformation products:

not measured

Reference 2

Endpoint:

biodegradation in water: sewage treatment simulation testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 2004-02-04 to 2004-09-22

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to other study

Qualifier:

according to guideline

Guideline:

OECD Guideline 303 A (Simulation Test - Aerobic Sewage Treatment. A: Activated Sludge Units)

Version / remarks:

2001-01-22

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Radiolabelling:

no

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Species: Activated sludge (micro-organisms) from a domestic waste water treatment plant was used.
- Origin: Activated sludge was supplied by the sewage plant Groß Zimmern, Germany.
- Preparation: An amount of 5 L waste water was taken from the aeration tank of the sewage treatment plant and the activated sludge was allowed to sediment in the laboratory. The sludge was washed three times using tap water and centrifuged between the washing steps. The sludge dry weight was determined to be 55.4 g/L. For the inoculation of the test units, 2 g sludge dry matter per litre organic medium was used (166 mL washed activated sludge per 4.6 L organic medium).

Duration of test (contact time):

81 d

Initial conc.:

25 mg/L

Based on:

DOC

Remarks:

phase I (day 0 to 22), total 22 days

Initial conc.:

30 mg/L

Based on:

DOC

Remarks:

phase II (day 22 to 43), total 14 days

Initial conc.:

15 mg/L

Based on:

DOC

Remarks:

phase III (day 43 to 57), total 18 days

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

The elimination and the primary and/or ultimate biodegradation of D-8 by aerobic micro-organisms were tested in a continuously operated test system simulating the activated sludge process according to OECD Guideline No. 303A. Domestic waste water as an easily biodegradable organic medium and the organic test item D-8 were the sources of carbon and energy for the activated sludge micro-organisms. Two parallel running laboratory scale waste water treatment test units aerated by pressurized air were used (control and D-8 treatment unit).
The test was conducted by coupling the test units by exchanging activated sludge daily (Coupling Units Test).

- Test units: according to the Husmann unit. The type behrotest© KA 1 consists of an aeration vessel (about 4.6 L volume) and a separator (secondary clarifier, about 2.6 L).
Control: approx. 40 L plastic containers
D-8 units: 10 L glass bottles with plastic lid were used until day 43, later on a stainless steel container (approx. 90 L) replaced the glass bottles

- For the stability of the organic medium, the containers were aerated by pressurised air and the organic medium containing the test item was continuously mixed by stirring bars (glass bottles) and agitator (stainless steel container). The outflow of the test units was collected in large plastic container (approx. 40 L) and periodically disposed.

Reference substance:

not required

Key result

% Degr.:

85

Parameter:

DOC removal

Sampling time:

81 d

Transformation products:

not measured

Evaporation of parent compound:

not measured

Volatile metabolites:

not measured

Residues:

not measured

Details on results:

Based on the results of this study it can be considered that D-8 is well biodegradable (primarily degradation, 85 % based on LOQ) and does not affect the activity of the activated sludge. A clear trend towards mineralisation of D-8 was indicated by the DOC-measurements, but did not allow a reliable quantification due to high background variations and the resolution power of the DOC method under the given test conditions.

DOC Removal Rates

The DOC influent concentrations of control varied between 20 mg/L and 192 mg/L. This was due to the fact that the waste water was sampled at different dates and therefore the composition differed as it is normal for domestic sewage. Depending on the D-8 amount added to the organic medium, the DOC in D-8 unit influent varied between 31 mg/L and 206 mg/L. However, the overall additional DOC due to D-8 addition was in the range of 7.2 to 22.8 mg DOC/L for the different test scenarios (based on the measured D-8 influent concentration).

The DOC removal of the control unit and D-8 unit were in the same range during the experiment with a wide variation noted for the different waste water batches used. Comparing the DOC removal of the control and the D-8 unit, a clear trend was observable over the entire study period. From the beginning of the test until the running-in period II (loading the D-8 unit with 30 mg D-8/L) the DOC removal of the control was above the DOC removal for the test unit in most cases. During the running-in period II the test unit showed tentatively higher rates than the control unit. This trend supports the assumption that mineralisation starts/takes place, even though the results do not allow a quantification. This can be explained by the fact that the change in DOC due to addition of D-8 compared to background DOC is too small to allow a reliable quantification. This trend is even more obvious for the plateau phase in which a high elimination rate (primary degradation measured by D-8 removal) is noted for D-8.

Although high variation was noted for the total DOC removal in both units (control and D-8 unit) due to high background variation, the D-8 removal based on DOC measurements was calculated. Those data further support the interpretation of the DOC removals described above:

- No indication for D-8 removal during running-in period I

- Trend towards mineralisation starting during running-in period II, potentially compromised by solubility problems

- Clear trend of mineralisation at the end of running-in period III and the following evaluation period

D-8 Elimination Rates

The coupling of the test units results in an exchange of D-8 between D-8 unit and control unit. Therefore, D-8 concentrations of influent and effluent were determined in each control and D-8 test unit, respectively. The D-8 concentration of control influent and effluent were below the limit of quantification. The D-8 elimination rates were calculated from the measured values in D-8 unit influent and effluent. The D-8 target concentration in the D-8 unit influent was varied throughout the experiment (25 mg/L, 30 mg/L and 15 mg/L). Until day 4 D-8 was mixed in adequate amounts to the organic medium storage tank. Afterwards a stock solution of D-8 in ethanol was prepared and filled into the storage tanks.

During the first 22 days the concentrations of D-8 in the effluent were slightly below the concentrations in the influent and did not decrease. Afterwards, particularly in the third stage of the running-in period, the D-8 concentration in the effluent decreased by time and was below the limit of quantification from day 54 onwards, clearly demonstrating a complete primary degradation.

The D-8 elimination started at about 36 to 39 days after application of the test item and increased more or less linearly with some values being outliner. The end of the linear phase and the beginning of the plateau phase was at about day 54. The outliner between days 40 and 47 might be explained by the solubility problems. After changing the D-8 loading to 15 mg/L (running-in period III) the elimination rates increased again. It can be assumed that in the running-in period II (30 mg/L) D-8 partially dropped out. In the following running-in period III (15 mg/L), the resolution of the dropped out D-8 can be assumed.

For the calculation of D-8 elimination from day 54 onwards the limit of quantification (2.5 mg D-8/L) as a worst case consumption was used, even though the real D-8 concentrations were below this limit. With the beginning of D-8 elimination on day 47 until the test end on day 81, in total 15 measurements were done.

Table: Elimination of D-8

Day	D-8 Concentration mg/L (mean value)		D-8 Elimination* %	Stages of Running
	Influent	Effluent
0	11.59	<2.50	78.4	running-in period I (22 days)
1	20.52	16.06	21.7
1	21.75	17.72	18.5
4	24.10	20.73	14.0
5	26.27	17.07	35.0
6	26.82	27.91	---
8	25.61	20.21	21.1
11	22.92	11.82	48.4
13	12.20	16.16	---
15	26.10	19.68	24.6
18	28.84	26.71	7.4
19	31.44	22.54	28.3
20	27.26	24.03	11.9
22	30.51	27.10	11.2
25	35.39	26.68	24.6	running-in period II  (14 days)
26	30.79	24.28	21.1
29	35.08	17.91	49.0
32	36.78	22.10	39.9
33	22.24	16.41	26.2
36	34.74	13.60	60.9
39	34.77	14.46	58.4
40	27.95	30.40	---
43	32.69	25.17	23.0	running-in period III (18 days)
46	15.83	17.69	---
47	16.49	13.53	18.0
49	17.63	5.45	69.1
54	16.47	2.50	84.8
55	15.13	2.50	83.5
57	19.69	2.50	87.3	evaluation period (27 days)
60	14.49	2.50	82.7
61	17.34	2.50	85.6
64	17.72	2.50	85.9
67	16.87	2.50	85.2
68	15.44	2.50	83.8
71	17.98	2.50	86.1
74	16.57	2.50	84.9
75	16.70	2.50	85.0
78	16.61	2.50	84.9
81	16.45	2.50	84.8

* = from influent / effluent plausible

--- = value not plausible

The D-8 removal curve does not indicate adsorbance effects since the D-8 elimination curve did not show a sharp increase. The degradation plot of D-8 shows lag, degradation and plateau phases.

Based on the results of this study it can be considered that D-8 is well biodegradable (primarily degradation, 85 % based on LOQ) and does not affect the activity of the activated sludge. A clear trend towards mineralisation of D-8 was indicated by the DOC-measurements, but did not allow a reliable quantification due to high background variations and the resolution power of the DOC method under the given test conditions.

Validity criteria fulfilled:

yes

Conclusions:

D-8 was tested for degradation in an aerobic sewage treatment simulation test in the laboratory according to OECD Guideline 303A. Based on the results of this study, it can be considered that D-8 is well biodegradable (primarily degradation, 85 % based on LOQ) and does not affect the activity of the activated sludge. A clear trend towards mineralisation of D-8 was indicated by the DOC-measurements.

Executive summary:

D-8 was tested for degradation in an aerobic sewage treatment simulation test in the laboratory according to OECD Guideline 303A. D-8 was tested at three concentration levels in three running-in phases (I, II and III). In running-in phase I D-8 was tested at 25 mg/L, concentration chosed to be below the solubility limit of 30 mg/L. The phase I was from day 0 until day 22. No indication of removal of D-8 during the phase I was observed. Therefore, in phase II the concentration of D-8 was increased to 30 mg/L. Some issues were observed at this concentration due to the different solubility on different waste waters. Nevertheless, a trend towards mineralisation starting was observed. The phase II was from day 22 to day 43. In phase III the D-8 concentration was reduced to 15 mg/L. Phase III was from day 43 to day 54. A clear trend of mineralisation was observed during this phase. Afterwards a 27-day evaluation period was run, up to day 81. Based on the results of this study, it can be considered that D-8 is well biodegradable (primarily degradation, 85 % based on LOQ) and does not affect the activity of the activated sludge. A clear trend towards mineralisation of D-8 was indicated by the DOC-measurements, but did not allow a reliable quantification due to high background variations and the resolution power of the DOC test method under the given test conditions. The results with regard to DOC-elimination in this Sewage Treatment Plant (STP) study are in line with the results of another study on ready biodegradation (see Sect. 5.2.1, FhG-Study 1990). In this Modified Sturm Test a mineralisation of up to 60 % of D-8 by activated sludge was seen for the given observation period of 39 days. This finding further supports that mineralisation of D-8 can be expected under STP conditions.

Description of key information

D-8 was tested for degradation in an aerobic sewage treatment simulation test in the laboratory according to OECD Guideline 303A. Based on the results of this study, it can be considered that D-8 is well biodegradable (primarily degradation, 85 % based on LOQ) and does not affect the activity of the activated sludge. A clear trend towards mineralisation of D-8 was indicated by the DOC-measurements.

Additional information

STP Simulation testing - OECD 303A

D-8 was tested for degradation in an aerobic sewage treatment simulation test in the laboratory according to OECD Guideline 303A. Based on the results of this study, it can be considered that D-8 is well biodegradable (primarily

D-8 was tested for degradation in an aerobic sewage treatment simulation test in the laboratory according to OECD Guideline 303A. D-8 was tested at three concentration levels in three running-in phases (I, II and III). In running-in phase I D-8 was tested at 25 mg/L, concentration chosed to be below the solubility limit of 30 mg/L. The phase I was from day 0 until day 22. No indication of removal of D-8 during the phase I was observed. Therefore, in phase II the concentration of D-8 was increased to 30 mg/L. Some issues were observed at this concentration due to the different solubility on different waste waters. Nevertheless, a trend towards mineralisation starting was observed. The phase II was from day 22 to day 43. In phase III the D-8 concentration was reduced to 15 mg/L. Phase III was from day 43 to day 54. A clear trend of mineralisation was observed during this phase. Afterwards a 27-day evaluation period was run, up to day 81. Based on the results of this study, it can be considered that D-8 is well biodegradable (primarily degradation, 85 % based on LOQ) and does not affect the activity of the activated sludge. A clear trend towards mineralisation of D-8 was indicated by the DOC-measurements, but did not allow a reliable quantification due to high background variations and the resolution power of the DOC test method under the given test conditions. The results with regard to DOC-elimination in this Sewage Treatment Plant (STP) study are in line with the results of another study on ready biodegradation (see Sect. 5.2.1, FhG-Study 1990). In this Modified Sturm Test a mineralisation of up to 60 % of D-8 by activated sludge was seen for the given observation period of 39 days. This finding further supports that mineralisation of D-8 can be expected under STP conditions.

Sediment simulation testing

The performance of simulation tests for biodegradation in sediment is scientifically not justified.

REACH Regulation (EC) No 1907/2006, Annex IX, Sect. 9.2.1.4., Col. 2, states as follows:

“9.2.1.4: The study need not to be conducted:

- if the substance is readily biodegradable, or

- if direct and indirect exposure of sediment is unlikely. ”

Direct and indirect exposure of the test item to sediment is unlikely. D-8 is manufactured and formulated in completely closed systems. Thus, direct and indirect exposure of the sediment compartment during manufacturing and formulation is practically negligible. Use of formulated D-8 is also unlikely to result in direct and indirect exposure to the sediment compartment. During use D-8 is included in three-dimensional matrices of resinous material and completely retained, therefore, no direct or indirect release of D-8 into the sediment compartment is expected. The test item is well degradable in aquatic systems and showed to be inherently biodegradable. Based on these results and the STP study, no other effects are expected in sediment.