2-Dibenzofuranyl-1-4,6-diphenyl-[1,3,5]-triazine

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:

Nov 14, 2019 - Jan 14, 2020

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

July 17, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

EEC Publication No. L 383 A, December 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany.

The aerobic activated sludge used for this study was deposited for 15 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.

Duration of test (contact time):

28 d

Initial conc.:

102.9 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

The mean biodegradation at test end after 28 days did not exceed 10% biodegradation throughout the test. At the end of the test, the degradation was 0% (ThODNH4) and therefore the 10 day window criterion was not passed.

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to 88% after 14 days and to 96% after 28 days of incubation.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The degradation rate of the test item did not reach 60 % within the 10-day window and after 28 days of incubation. Thus, the test item is not readily biodegradable.

Executive summary:

Purpose

The purpose of this study was to determine the ready biodegradability of the test item.

Methods

The information for this endpoint study record was obtained from an experimental study. The OECD GLP criteria were met and the methods applied are fully compliant with OECD TG  301F.
The test item was exposed to aerobic activated sludge from the aeration tank of a domestic waste water treatment plant for 28 days. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. As a reference item sodium benzoate was tested simultaneously under the same conditions as the test item, and functioned as a procedure control. This type of study is recognized by the international test guidelines and should provide a rational basis to assess the ready biodegradation properties of the test item when incubated with aerobic activated sludge.

Results

Nitrogen is part of the molecular structure of the test item; therefore the evaluation of biodegradation has to be based on ThODNH4 and ThODNO3. The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10 -day window; the 10 -day window starts when the degradation of the test item reaches at least 10% degradation.

The test material never reached 10%. The mean biodegradation at test end after 28 days was 9% (ThODNH4) and 7% (ThODNO3).

Therefore, the test material is considered to be not readily biodegradable based on ThODNH4 and ThODNO3.

The reference item sodium benzoate was sufficiently degraded to 88% after 14 days and 96% after 28 days of incubation, thus confirming the suitability of the aerobic activated sludge inoculum used.

In the toxicity control containing both, the test item and the reference item sodium benzoate, 33% (ThODNH₄) biodegradation was noted within 14 days and 37% (ThODNH₄)

after 28 days of incubation. According to the test guidelines, the test item can be assumed to be not inhibitory to the aerobic activated sludge microorganisms because degradation was >25% within 14 days.

Conclusion

Under the conditions of this study the test item is considered to be not readily biodegradable.

Description of key information

OECD 301F: not readily biodegradable

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater