4-(4-isopropoxyphenylsulfonyl)phenol

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 1990-04-18 to 1990-07-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.4-C (Determination of the "Ready" Biodegradability - Carbon Dioxide Evolution Test)

Version / remarks:

Modified Sturm Test

Deviations:

yes

Remarks:

testing time was 39 days instead of 28 days

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test)

Version / remarks:

Modified Sturm Test

Deviations:

yes

Remarks:

testing time was 39 days instead of 28 days

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

Source of the test inoculum was activated sludge of a small municipal sewage treatment plant, mainly fed with domestic sewage.
Pre-treatment of inoculum:
The activated sludge was aerated for 4 hours. 500 mL was sampled and homogenized for 2 minutes and then settled for 30 minutes. The supernatant was adjusted to an extinction value (436 nm) of 0.2. This density represents a CFU (Colony Forming Units) of about 10E6 microorganisms per millilitre. 30 mL of this suspension were used as inoculum for each CO2 flask.

Duration of test (contact time):

39 d

Initial conc.:

ca. 10 mg/L

Based on:

test mat.

Initial conc.:

ca. 20 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

The test material was added to a chemically defined liquid medium, inoculated with sewage microorganisms and aerated with CO2-free air at 20 - 25 °C in a temperature controlled room. The temperature was controlled during the test period.
The released CO2 was trapped as BaCO3, and the degradation was followed by CO2 analysis over a period of 39 days. After reference to suitable blank control(s), the total amount of CO2 produced by the test compound was determined for the test period and calculated as a percentage of the CO2 that the test material, based on its carbon content, could have theoretically produced.
The procedure was checked by means of a reference substance.

Reference substance:

aniline

Remarks:

concentrations: 10 mg/L; 20 mg/L

Test performance:

As the degradation was not finished at day 28 the test period was prolonged for further 11 days.

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 60

Sampling time:

39 d

Remarks on result:

other: at test item concentration 10 mg/L

Key result

Parameter:

% degradation (CO2 evolution)

Value:

ca. 31

Sampling time:

39 d

Remarks on result:

other: at test item concentration 20 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

ca. 45

Sampling time:

28 d

Remarks on result:

other: at test item concentration 10 mg/L

Parameter:

% degradation (CO2 evolution)

Value:

ca. 31

Sampling time:

28 d

Remarks on result:

other: at test item concentration 20 mg/L

Details on results:

A typical exponential phase of degradation was not obtained. Until day 20 a slow degradation at both concentrations was observed. Thereafter, a diauxic behaviour was obtained for the concentration 10 mg/L, whereas at the concentration of 20 mg/L the degradation stopped. Finally, degradation rates of 60 % (10 mg/L) and 31 % (20 mg/L) were obtained.

Results with reference substance:

Typical degradation curves were obtained at both concentrations. Finally, degradation rates of 100 % (10 mg/L) and 94 % (20 mg/L) were obtained.

Table 1: CO2 -production and % degradation of the test item at 10 and 20 mg/L

Day	Test Substance – 10 mg/L			Day	Test Substance – 20 mg/L
	CO2 tit. mg	Sum CO2 mg	% Degrad. (% ThCO2)		CO2 tit. mg	Sum CO2 mg	% Degrad. (% ThCO2)
1	0.48	0.48	0.70	1	0.00	0.00	0.00
2	0.74	1.22	1.79	2	0.11	0.11	0.08
3	0.69	1.90	2.81	3	0.26	0.37	0.27
4	1.06	2.96	4.37	4	1.69	2.06	1.52
5	0.57	3.53	5.21	5	1.61	3.67	2.71
6	1.04	4.57	6.74	6	1.87	5.53	4.08
7	1.54	6.11	9.01	7	2.43	7.96	5.87
8	1.43	7.54	11.13	8	1.76	9.72	7.17
9	1.00	8.54	12.59	9	2.25	11.98	8.83
10	2.46	11.00	16.23	10	3.30	15.28	11.27
11	1.10	12.10	17.85	11	2.77	18.05	13.31
13	1.68	13.78	20.32	13	3.56	21.61	15.94
15	0.05	13.83	20.40	15	1.72	23.33	17.21
18	2.19	16.02	23.63	18	4.59	27.92	20.59
20	2.66	18.69	27.56	20	5.05	32.98	24.32
22	2.83	21.51	31.73	22	4.67	37.65	27.77
25	4.36	25.87	38.16	25	3.54	41.19	30.38
27	4.88	30.75	45.36	27	1.30	42.50	31.34
29	2.90	33.65	49.63	29	0.00	42.50	31.34
32	2.41	36.06	53.18	32	0.00	42.50	31.34
33	0.92	36.97	54.53	33	0.00	42.50	31.34
36	2.10	39.07	57.63	36	0.00	42.50	31.34
39	1.62	40.69	60.01	39	0.00	42.50	31.34

At the 27th day at a concentration level 10 mg/L the test item was degradated at 45.36 % and at concentration level 20 mg/L - at 31.34 %. At the lower concentration the biodegradation continued steadily to increase and reached 60 % after 39 days of exposure. It is clear that after a lag phase the test item starts to degrade increasingly but did not reach the level of 60 % within the 28 days of exposure, therefore, the test item is not considered as readily biodegradable. As more than 20 % in the exposure period were reached at both concentration levels, it can be stated that the test item is inherently biodegradable.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable, fulfilling specific criteria

Conclusions:

In the test, D-8 reached 60 % biodegradation at the end of the 39-days exposure. During the guideline 28-days exposure period, D-8 reached 31 to 45 % biodegradation, therefore, the test item is considered to be inherently biodegradable.

Executive summary:

D-8 was tested of aerobic degradability in a static activated sludge test (CO2 evolution test) according to EU Test guideline C.4-C and OECD 301B. The biodegradation was followed by determination of the evolved CO2. Sludge from a domestic sewage treatment plant was exposed to the test item for 39 days at two concentration levels – 10 and 20 mg/L. The validity of the test was shown by degradation of a reference substance (aniline) tested at 10 and 20 mg/L. The reference item degradation rates were 100 % at 10 mg/L and 94 % at 20 mg/L, respectively. A typical exponential phase of degradation of the test item was not obtained. Until day 20 a slow degradation at both concentrations was observed. Thereafter, a diauxic behaviour was obtained for the concentration 10 mg/L, whereas at the concentration of 20 mg/L the degradation stopped. D-8 showed degradation rates after 39 days of 60 % at a concentration of 10 mg/L and 31 % at 20 mg/L. Based on the results obtained, D-8 was regarded as inherently biodegradable.

Description of key information

In the test, D-8 reached 60 % biodegradation at the end of the 39-days exposure. During the guideline 28-days exposure period, D-8 reached 30 to 45 % biodegradation, therefore, the test item is considered to be inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

inherently biodegradable, fulfilling specific criteria

Type of water:

freshwater

Additional information

D-8 was tested of aerobic degradability in a static activated sludge test (CO2 evolution test) according to EU Test guideline C.4-C and OECD 301B. The biodegradation was followed by determination of the evolved CO2. Sludge from a domestic sewage treatment plant was exposed to the test item for 39 days at two concentration levels – 10 and 20 mg/L. The validity of the test was shown by degradation of a reference substance (aniline) tested at 10 and 20 mg/L. The reference item degradation rates were 100 % at 10 mg/L and 94 % at 20 mg/L, respectively. A typical exponential phase of degradation of the test item was not obtained. Until day 20 a slow degradation at both concentrations was observed. Thereafter, a diauxic behaviour was obtained for the concentration 10 mg/L, whereas at the concentration of 20 mg/L the degradation stopped. D-8 showed degradation rates after 39 days of 60 % at a concentration of 10 mg/L and 31 % at 20 mg/L. Based on the results obtained, D-8 was regarded as inherently biodegradable.