tert-butyl peracetate

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:

1999-10-14 and 2000-03-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Version / remarks:

1992

Deviations:

yes

Remarks:

test was prolonged up to 112 days; instead of an effluent/extract/mixture, activated sludge was used as an inoculum

Qualifier:

according to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Version / remarks:

1984

Deviations:

yes

Remarks:

test was prolonged up to 112 days; activated sludge was used

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

Secondary activated sludge was obtained from WWTP Nieuwgraaf in Duiven, The Netherlands. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 200 mg Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted to a concentration of 2 mg DW/L in the BOD bottles. The dry weight (DW) of the inoculum was determined by filtrating 50 mL of the activated sludge over a pre-weighed 12 µM Schleicher und Schüll filter (dried for 1.5 hours at 104 °C and weighed after cooling).

Duration of test (contact time):

112 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4 * 2H2O, 22.5 mg MgSO4 * 7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3 * 6H2O per litre of deionized water
- Solubilising agent: dichlormethane (1 g/L)
- Test temperature: 20 +/- 1 °C
- pH: 6.7 to 6.9 at the start of the test
- pH adjusted: no
- Other: Ammonium chloride was not added to the medium to prevent nitrification. The pH of the medium decreased slightly due to this absence of ammonium. The decrease of the pH does not affect the biodegradation in the Closed Bottle test.
Sodium acetate was added to the bottles using a stock solution of 1.0 g/L. The test substance in dichlormethane was added to 2 g silica gel (100-200 mesh) weighed in a glass petri dish. The solvent was allowed to evaporate by placing the petri dish in a ventilated hood for 3 hours, and the entire contents were then transferred to the BOD bottle. The dissolved oxygen concentrations were determined electrochemically using an oxygen electrode (WTW Trioxmatic EO 200) and meter (WTW OXI 530). The pH was measured using a Consort pH meter (Salm en Kipp BV, Breukelen, The Netherlands). The temperature was and recorded with a thermo couple connected to a data logger.

TEST SYSTEM
- Culturing apparatus: 250 to 300 mL BOD bottles with glass stoppers
- Number of culture flasks/concentration: 10 bottles - only inoculum, 10 bottles - test substance + inoculum, 10 bottles - sodium acetate + inoculum
- Measuring equipment: The oxygen electrode was inserted in the BOD bottle to measure the oxygen concentration and the medium displaced by the electrode was collected in the funnel.

SAMPLING
- Sampling frequency: Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21 and 28.

CONTROL AND BLANK SYSTEM
- Inoculum blank: 10 bottles containing only nutrient medium and the inoculum.

Reference substance:

other: sodium acetate trihydrate

Preliminary study:

no preliminary study

Key result

Parameter:

% degradation (O2 consumption)

Value:

4

Sampling time:

28 d

Details on results:

The calculated theoretical oxygen demand of the test material was 2.7 mg/mg. The ThOD of sodium acetate was 0.8 mg/mg.
Possible inhibitory effects of the respiration of the inoculum by the test substance were investigated. The results indicated, that no inhibition of the biodegradation due to the "high" intial concentration of the test compound is expected.

Results with reference substance:

The biodegradation of the reference substance was 69 % after 14 days.

Validity criteria fulfilled:

not specified

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The biodegradation of the test substance was 4 %. Therefore, the test substance was not biodegraded in the closed bottle test.

Executive summary:

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test according to slightly modified OECD and EEC Guidelines, and in compliance with the OECD principles of Good Laboratory Practice. In the biodegradability tests, microorganisms are inoculated into a chemically defined liquid medium containing the test substance as sole carbon and energy source. The test compound is exposed to the inoculum, consisting of relatively low numbers of microorganisms from an activated sludge plant, under aerobic conditions for a period of at least 28 days.The test was prolonged because the pass level was not reached at day 28. The test substance caused no reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. The biodegradation of the test substance was 4 %. Hence, the test substance was not biodegraded in the Closed Bottle test (28 days and prolonged) and should therefore not be classified as readily biodegradable. The reference substance, sodium acetate, was degraded 69 % of its theoretical oxygen demand after 14 days.

Description of key information

The biodegradation of the test substance was 4 %. Hence, the test substance was not readily biodegradable in the Closed Bottle test (28 days and prolonged).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test according to slightly modified OECD and EEC Guidelines, and in compliance with the OECD principles of Good Laboratory Practice. In the biodegradability tests, microorganisms are inoculated into a chemically defined liquid medium containing the test substance as sole carbon and energy source. The test compound is exposed to the inoculum, consisting of relatively low numbers of microorganisms from an activated sludge plant, under aerobic conditions for a period of at least 28 days.The test was prolonged because the pass level was not reached at day 28. The test substance caused no reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum.The biodegradation of the test substance was 4 %. Hence, the test substance was not biodegraded in the Closed Bottle test (28 days and prolonged) and should therefore no be classified as readily biodegradable. The reference substance, sodium acetate, was degraded 69 % of its theoretical oxygen demand after 14 days.