4-tert-butylpyrocatechol

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: inherent biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 7 sept 2009 to 9 dec 2009

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2009

Report date:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.9 (Biodegradation: Zahn-Wellens Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

4-tert-butylpyrocatechol

EC Number:

202-653-9

EC Name:

4-tert-butylpyrocatechol

Cas Number:

98-29-3

Molecular formula:

C10H14O2

IUPAC Name:

4-tert-butylbenzene-1,2-diol

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Laboratory culture: no, aerobic activated sludge came from a wastewater treatment plant (ARA Ergolz II, Füllinsdorf / Switzerland).
- Method of cultivation: During the holding period of one day prior to use, the sludge was aerated at room temperature.
- Preparation of inoculum for exposure: The sludge was washed three times with tap water by centrifugation and the supernatant liquid phase was decanted. Calculated amounts of wet sludge were suspended in test water to obtain a concentration equivalent to 4 g (±10%) dry material per liter.
- Concentration of sludge: 300 mg dry material per liter
- Initial biomass concentration: 4 g dry material per liter

Duration of test (contact time):

28 d

Initial test substance concentration

Initial test substance concentration 1

Initial conc.:

143 mg/L

Based on:

test mat.

Initial test substance concentration 2

Initial conc.:

ca. 86 mg/L

Based on:

DOC

Parameter followed for biodegradation estimation

Parameter followed for biodegradation estimation:

DOC removal

Details on study design:

TEST CONDITIONS
- Composition of medium: 10 mL of the stock solution: KH2PO4 (8.50 g/L) + K2HPO4 (21.75 g/L) + Na2HPO4, 2H2O (33.40 g/L) + NH4Cl (0.50 g/L) and 1 mL each of stock solutions: MgSO4, 7H20 (22.50 g/L) - CaCl2, 2H2O (36.40 g/L) - FeCl3, 6H2O (0.25 g/L), were combined and made up to 1000 mL with purified water.
- Test temperature: 21 - 24°C
- pH: 6.7 - 7.5 (before adjustment)
- pH adjusted: yes
- Aeration of dilution water: yes
- Continuous darkness: yes
- Oxygen concentration: 7.6 - 8.3 mg O2/L


TEST SYSTEM
- Culturing apparatus: Erlenmeyer flask
- Method used to create aerobic conditions: Each flask was loosely covered with aluminium foil to allow the exchange of air between the flask and the surrounding atmosphere. The test media were continuously stirred by magnetic stirrers.


SAMPLING
- Sampling frequency: exposure day 0 (0 and 3 hours ± 30 minutes after the addition of the test chemical), 3, 7, 10, 14, 21 and 28
- Sampling method: Prior to sampling, water evaporation losses were compensated by adding purified water up to the mark. Deposits on the test vessels were resuspended in the test vessels. Per sampling interval, one sample of about 10 mL was taken and analyzed for DOC on the day of sampling. Samples were filtered through a 0.45 µm filter. The first 3–4 mL of the filtrate were discarded.


CONTROL AND BLANK SYSTEM
- Inoculum blank: yes; DOC of inoculum control: mean 4.1 mg/L (n=2)
- Abiotic sterile control: no
- Toxicity control: yes; DOC of toxicity control: 172.8 mg/L


STATISTICAL METHODS: no

Reference substance

Reference substance:

diethylene glycol

Results and discussion

% Degradation

Key result

Parameter:

% degradation (DOC removal)

Value:

91

Sampling time:

28 d

Details on results:

No DOC removal was observed during the first three hours of exposure which is an indication that the test item did not adsorb on activated sludge.
In the toxicity control, containing the test item, the reference item diethylene glycol and activated sludge (inoculum), the initial DOC decreased by 81% within 14 days of exposure. Thus, according to the test guidelines the test item was not inhibitory to activated sludge at the tested concentration of 143.5 mg/L beacause degradation was > 35% within 14 days.
In the test flasks containing the test item and activated sludge (inoculum) the mean concentration of DOC (dissolved organic carbon) continuously decreased from initially 86 mg/L on Day 0 (starting value after 3 hours of exposure) to 7 mg/L on Day 28. The mean biodegradation of 4-tert-butylpyrocatechol (4-TBC), based on DOC decrease, amounted to 91% after 28 days. Consequently, 4-Tert-Butylpyrocatechol (4-TBC) was found to be biodegradable by 91% under the test conditions within 28 days.
No DOC removal was observed during the first three hours of exposure which is an indication that the test item did not adsorb on activated sludge.

BOD5 / COD results

Results with reference substance:

In the procedure control containing the reference item diethylene glycol and activated sludge (inoculum), the reference item was completely degraded within the first seven days of exposure, thus confirming suitability of the activated sludge.

Any other information on results incl. tables

Table 1: Percentage biodegradation of the test item and the reference item

	Percentage Biodegradation^1, 2
	Test item: 4-TBC^2			Procedure control: Diethylene glycol			Toxicity control
Time	Replicate No.			Replicate No.			Replicate No.
(days)	1	2	Mean	1	2	Mean	1
0	0	0	0	0	0	0	0
3	62	65	64	36	25	31	--
7	84	77	80	100	102	101	71
10	91	77	84	--	--	--	--
14	89	91	90	101	98	99	81
21	95	92	93	--	--	--	--
28	95	88	91	99	100	100	79

¹          Corrected for the inoculum controls

²          0 days = 3 hours ± 30 minutes after the addition of the test item

--         Not determined

 

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

More that 70% degradation of the test item 4-tert-butylpyrocatechol (4-TBC) occurred within the first seven days of the test, including the lag-phase and the log-phase. The log-phase was lower than 3 days.
Therefore, 4-TBC could be considered as inherent ultimately biodegradable according to OECD (2006).

Executive summary:

In a study (Harlan study, C60372, 2009), the inherent biodegradability of 4 -tert-butylpyrocatechol (4 -TBC) (initial concentration: 143 mg/L), was tested in a Zahn-Wellens test during 28 days, according to OECD guideline for Testing of Chemicals n°302B (1992).

Inoculum used in a study was 300 mg/L of a sludge from a wastewater treatment plant, adapted.

The percentage of biodegradation was estimated by following the DOC removal.

4 -TBC did not adsorb on activated sludge.

4 -TBC was not inhibitory to activated sludge at the tested concentration of 143.5 mg/L because degradation was > 35% within 14 days.

The corresponding percentage of biodegradation obtained was 91% of DOC removal after 28 days.

Under the test conditions, 4 -TBC is considered as inherent ultimately biodegradable.

More that 70% degradation of 4 -TBC occurred within the first seven days of the test, including the lag-phase and the log-phase. The log-phase was lower than 3 days.

This study is classified as acceptable and satisfies the guideline requirements for inherent biodegradability study (OECD 302B).