2,6-di-tert-butylphenol

Biodegradation in water: screening tests

Description of key information

12-24% degradation within 28 days  (% of COD) and 8-17% degradation (% ThOD). COD = 2.06 mg O2/mg (OECD 302 C)

Additional information

Three studies have been conducted evaluating the ready biodegradation of 2,6-di-tert-butylphenol.

·        inherent biodegradability

·        anaerobic aquatic biodegradation

·        ready biodegradability

In the key study, 2,6-di-tert-butylphenol was evaluated for its inherent biodegradability. The test substance attained between 12-24% degradation within 28 days calculated from oxygen uptake (% of COD) and between 8-17% degradation (% ThOD) and cannot, therefore, be considered as inherently biodegradable under the strict terms and conditions of the OECD Guidelines.

 

Test method:

The method used followed that described in the OECD Guidelines for Testing of Chemicals / Section 2: Degradation and Accumulation, Test No. 302C "Inherent Biodegradability, Modified MITI Test (II)". A mixed population of activated sewage sludge microorganisms was used as inoculum and aniline as reference substance. Initial concentration of test substance was 30 mg/l and reference substance 100 mg/l. TOC analysis of 2,6-di-tert-butylphenol was not possible due to the insoluble nature of the test material. A modified MITI test was carried out due to this fact. A COD value of 2.06 mg O₂/mg was obtained for the test material.

A study was conducted to assess the anaerobic aquatic biodegradation. Under the conditions of this study, 2,6-di-tert-butylphenol did not biodegrade.

Test method:

The anaerobic aquatic metabolism of ¹⁴C-2,6-di-tert-butylphenol was investigated in primary sludge from an anaerobic digestor, representative of an intended 2,6-di-tert-butylphenoluse site according to EPA OTS 796.3140 (Anaerobic Biodegradability of Organic Chemicals) guideline. At weekly sampling intervals over a 56 day study, aliquots of the sludge were analyzed to determine the rate of biodegradation of ¹⁴C-2,6-di-tert-butylphenol. Results of this study determined that 2,6-di-tert-butylphenol did not degrade under the conditions of this study. The reference material, ethanol, demonstrated significant degradation.

A further study was conducted to assess the ready biodegradability of2,6-di-tert-butylphenol using the Modified Sturm Test.

Test method:

The purpose of the study was to measure the test substance's ready biodegradability as measured by CO₂ formation in percent of theoretical CO₂calculated from the total organic carbon content in accordance with OECD Guideline 301 B (Ready Biodegradability: CO₂Evolution Test). The test substance was cultured with bacteria collected from a sewage treatment plant and CO₂evolution was measured. Aniline was used as a positive control for this study. Results of the test showed that 2,6-di-tert-butylphenol is not readily biodegradable as measured by this method.