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Environmental fate & pathways

Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Study period:
23/6/2011-23/8-2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Guideline study with GLP accreditation
Reason / purpose:
reference to other study
Qualifier:
according to
Guideline:
OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)
Deviations:
yes
Remarks:
See below
Principles of method if other than guideline:
One deviation introduced from the guidelines of the Closed Bottle test was;ammonium chloride was not added to prevent oxygen consumption due tonitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound). The test was also extended to 60 days.
GLP compliance:
yes (incl. certificate)
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, non-adapted
Details on inoculum:
Activated sludge (17-06-2011) was obtained from the wastewater treatment plant Nieuwgraaf in Duiven, The Netherlands. This activated sludge plant treats predominantly domestic wastewater. The activated sludge was preconditioned to reduce the endogenous respiration rates. To this end, 400 mg Dry Weight (DW)/L of activated sludge was aerated for one week. The sludge was diluted in the BOD bottles (van Ginkel and Stroo, 1992).
Duration of test (contact time):
60 d
Initial conc.:
2 mg/L
Based on:
ThOD/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
The Closed Bottle test was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). The test substance in dichloromethane (0.6 mL) was directly added to bottles. Dichloromethane (0.6 mL) was added to a series of control bottles. The solvent was allowed to evaporate by placing the bottles on a roller bank in a ventilated hood for 24 hours to obtain an even distribution of the test substance on the walls of the bottles. Use was made of 10 bottles containing only inoculum (not agitated), 6 bottles containing inoculum and sodium acetate (not agitated), 10 bottles containing inoculum and test substance (agitated), and 10 bottles treated with dichloromethane (added and evaporated) only containing inoculum (agitated). The contents of bottles were agitated with magnetic stirrers at 600 rpm. The concentrations of the test substance and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28. One extension from the protocol of the Closed Bottle test was introduced. The Closed Bottle test was prolonged by measuring the course of the oxygen decrease in the bottles of day 28 using a special funnel. This funnel fitted exactly in the BOD
bottle. Subsequently, the oxygen electrode was inserted in the BOD bottle to measure the oxygen concentration. The medium dissipated by the electrode was collected in the funnel. After withdrawal of the oxygen electrode the medium collected flowed back into the BOD bottle, followed by removal of the funnel and closing of the BOD bottle (van Ginkel and Stroo 1992).
Preliminary study:
No information
Test performance:
Validity of the test
The validity of the test is demonstrated by an endogenous respiration of 0.8mg/L at day 28 . Furthermore, the differences of the replicate values at
day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 85. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.
Parameter:
% degradation (O2 consumption)
Value:
21
Sampling time:
28 d
Parameter:
% degradation (O2 consumption)
Value:
25
Sampling time:
60 d
Details on results:
The test material is not readily biodegradable. Due to the extension of the test to 60 days there are strong indications that the test substance is
inherently biodegradable due to 25% degradation taking place.
Results with reference substance:
The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 85.

Toxicity

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test compound in the Closed Bottle test was not determined because possible toxicity of 1,1,3,3-tetramethylbutyl peroxyneodecanoate to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance tested was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial concentration of the test compound is expected.

Validity criteria fulfilled:
yes
Interpretation of results:
inherently biodegradable
Conclusions:
The test can be concluded as reliable without restrictions.
Executive summary:

Guideline study with justified deviations. GLP accreditation given and sufficient test substance identification present. Validity criteria for the study were also met.

Description of key information

1,1,3,3-Tetramethylbutyl peroxyneodecanoate is biodegraded by 21% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this compound was biodegraded 25% at day 60. 1,1,3,3-Tetramethylbutyl peroxyneodecanoate is not readily biodegradable. The
biodegradation reached at the last day of the test demonstrates that this test substance should be classified as inherently biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
inherently biodegradable

Additional information

The parent chemical is known to hydrolyze (5.1.2) thermically degrade (SADT 15ºC) . This would have also been the case in the biodegradation test. The subsequently formed degradation products however do not fully degrade. Identification of potential degradation products has been investigated. See section on additional ecotoxicological information. 1,1,3,3-Tetramethylbutyl peroxyneodecanoate is biodegraded by 21% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test this compound was biodegraded 25% at day 60. 1,1,3,3-Tetramethylbutyl peroxyneodecanoate is not readily biodegradable. The biodegradation reached at the last day of the test demonstrates that this test substance should be classified as inherently biodegradable.