A method for measuring the anoxic biodegradability under denitrifying conditions.

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Environmental chemistry

Background:

• Assessing the biodegradability of organic compounds is crucial for environmental risk assessment.
• Standard biodegradability tests often focus on aerobic conditions, potentially overlooking anoxic processes.
• Understanding xenobiotic compound fate under denitrifying conditions is vital for contaminated site remediation.

Purpose of the Study:

• To propose and validate a novel method for assessing the anoxic biodegradability of organic compounds under denitrifying conditions.
• To evaluate sediment extracts as a suitable inoculum source for anoxic biodegradability tests.
• To compare the biodegradability of xenobiotic compounds (aniline, phenol) under anoxic denitrifying and aerobic conditions.

Main Methods:

• Development of a test method based on CO2 recovery and quantification as evidence of complete biodegradation.
• Utilizing a mineral medium with nitrate as the electron acceptor.
• Assessing inoculum sources (whole lake sediments, sediment extracts, commercial inoculum) using glucose biodegradability tests.
• Testing xenobiotic compounds (aniline, phenol) under both anoxic denitrifying and standard aerobic conditions.

Main Results:

• Sediment extracts were identified as a suitable and environmentally relevant inoculum source, contributing minimal carbon.
• Aniline and phenol demonstrated ready biodegradability (>60% degradation within 28 days) under anoxic denitrifying conditions.
• Biodegradation kinetics under anoxic conditions were slower than aerobic conditions, with potential intermediate metabolite accumulation for phenol.

Conclusions:

• The proposed test effectively assesses anoxic biodegradability under denitrifying conditions.
• Xenobiotic compound fate under anoxic conditions can differ significantly from aerobic environments.
• Standard biodegradability testing procedures should consider anoxic conditions for a comprehensive environmental assessment.