Cyclohexanamine, 4,4’-methylenebis[N-(2,2-dimethyl-3-(4-morpholinyl)propylidene)]-

Biodegradation in water: screening tests

Description of key information

In a Closed Bottle Test according to OECD TG 301 D the substance was determined to be not readily biodegradable (8.0 % biodegradation on day 28).

Key value for chemical safety assessment

Biodegradation in water:

not biodegradable

Type of water:

freshwater

Additional information

 

To determine the ready biodegradability of the test item a Closed Bottle Test according to OECD TG 301 D and EU Method C.4-E was carried out in accordance with the GLP principles. The test item was investigated at the concentration of 2.5 mg/L and exposed in duplicates to activated sludge from the aeration tank of a domestic waste water treatment plant in completely full and closed bottles in the dark at controlled temperature (22 ± 2 °C) for 28 days. The test item concentration was chosen based on the performed preliminary experiments: on solubility properties, behaviour, and toxicity of the test item; furthermore, on the calculated ThOD_NH4 value of the test item (ThOD_NH4 calculated according to equation given in the guidelines, assuming that no nitrification occurs) of 2.54 mg O₂/mg. In parallel (under the same conditions as the test item), positive reference item, sodium benzoate at the concentration of 3.0 mg/L (as procedure control), inoculum control and toxicity control were investigated. The biodegradation was followed by the oxygen uptake of the microorganisms during exposure. The percentage biodegradation of the reference item confirmed the suitability of the used activated sludge inoculum. As a result, no ready biodegradation of this test item was noticed. After 28 days only 8.0 % of the test item were biodegraded (mean, measured based on its theoretical oxygen demand (ThOD_NH4)). Based on the results of the analytical determination of possible nitrite and nitrate development, oxygen uptake resulting from a possible ammonium oxidation did not influence the amount of oxygen taken up by microbial population. Consequently, any correction of the measured dissolved oxygen concentrations was not performed. The biodegradability value of the test item was calculated based on its ThOD_NH4; any correction, based on the measured nitrite nitrate content was not performed. In conclusion, the test item is considered to be not readily biodegradable, as the pass level for ready biodegradability of 60 % removal based on the theoretical oxygen demand (ThOD_NH4) within a 10-day window was not met. However, according to the test guidelines the test item can be assumed as not inhibitory at the applied concentration level on the activated sludge microorganisms because the degradation in the toxicity control was higher than 25 % within 14 days. All validity criteria of the test guidelines were fulfilled; the test is hence considered valid.