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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

Not readily biodegradable

Key value for chemical safety assessment

Additional information

The ready biodegradability of the test item was assessed in a 28-day biodegradation test following the “Manometric Respirometry” method according to the OECD guideline 301F.

For this purpose, the test item was added to activated sludge collected from the aeration tank of a civil wastewater treatment plant and let to stay in contact with the sludge for 28 days under continuous stirring.

The tested concentration was 100 mg/L as test item. The biodegradation was followed by measuring the BOD (Biochemical Oxygen Demand) of the test item under defined conditions by means of a manometric method.

The test item is considered to be stable at the test conditions for a time corresponding to the exposure time (28 days). Therefore, all reported results are related to the nominal concentration of the test item.

The ThOD NH3 values were calculated to be equal to 1.67 mg O2/mg for reference item and 0.79 mg O2/mg for test item.

According to OECD guideline no. 301, the oxygen consumption due to nitrification was not considered since the test substance does not contain N.

The test complies with the validity criteria since the mean oxygen uptake in the inoculum control at the end of test period was 40 mg O2/L and there was not difference between duplicate values of test item degradation at the end of the test period. Moreover, the reference item reached the biodegradation pass level (60%) on the sixth day (65.3%). The test item 3,4-dichlorobenzotrichloride was found to be not readily biodegradable under the conditions applied in a Manometric Respirometry test, having not showed biodegradation during the test period. Even so, the test item did not show any inhibitory effects on the microorganism activity at the tested concentration as demonstrated by the 25% of biodegradation exceeded in the toxicity control already at third day of test period (41.9%).