Phenol, 4-amino-, reaction products with 4-(2-naphthalenylamino)phenol and sodium sulfide (Na2(Sx))

Biodegradation in water: screening tests

Description of key information

The test item was considered to be not readily biodegradable (6.0 % biodegradation on day 28). According to the test guidelines the pass level for ready biodegradability is 60 % of COD.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

The ready biodegradability of the test item was assessed under GLP conditions according to OECD TG 301 D, EU Method C.4.and EPA Guideline 712-C-98-076: OPPTS 835.3110. The test item was exposed to activated sludge from the aeration tank of a domestic waste water treatment plant. The biodegradation was followed by oxygen uptake of the microorganisms during exposure. As a reference item Sodium benzoate (at a concentration of 3.0 mg/L) was tested simultaneously under the same conditions as the test item, and functioned as a procedure control (reference control). Additionally inoculum (containing the filtered inoculum only) and toxicity (containing both the test item and reference item) controls were examined.The chosen test item concentration of 3.0 mg/L investigated in the main test was based on the results of the preliminary solubility and toxicity tests. The chemical oxygen demand(COD) of 1.82 mg O2/ mg test item was determined at the start of the main experiment. Under the test conditions ready biodegradation of this test item was not observed. The percentage biodegradation of the test item reached a mean of 6.0 % after 28 days based on its COD. Based on the dissolved oxygen depletion, the resulting biodegradation values reached a plateau on about the 7thday of the experiment. From this day the slight changes were considered as being within the biological variability range of the applied test system. The concurrently conducted analytical determination of possible nitrite and nitrate development showed slight changes in nitrite concentrations in the 28-day samples; however the measured dissolved oxygen concentrations in the inoculum control, test item and toxicity control bottles did not correspond to the consumed oxygen of ammonium oxidation processes.Likely technical effects (turbidity and/or discoloration) also influenced the nitrite concentration determinations. Therefore, the biodegradability value of the test item was calculated based on its COD; any correction, based on the measured nitrite and/or nitrate content was not performed. The reference item Sodium benzoate was sufficiently degraded to a mean of 79.7 % after 14 days, and to a mean of 82.8 % after 28 days of incubation, based on ThODNH3, thus confirming the suitability of the used activated sludge inoculum. In the toxicity control containing both, the test item and the reference item, a mean of 37.8 % biodegradation was noted within 14 days and 42.4 % biodegradation after 28 days of incubation. Thus, the test item can be assumed to not inhibit the activated sludge microorganisms (higher than 25 % degradation occurred within 14 days).