Batch and continuous biodegradation of three model naphthenic acids in a circulating packed-bed bioreactor

Area of Science:

• Environmental Science
• Biotechnology
• Chemical Engineering

Background:

• Oil sands processing generates naphthenic acid-contaminated water, posing environmental risks.
• Sustainable water management necessitates effective treatment technologies like bioremediation.

Purpose of the Study:

• To investigate the biodegradation of specific naphthenic acids using a lab-developed microbial culture.
• To evaluate the performance of a circulating packed bed bioreactor for treating contaminated process water.

Main Methods:

• Utilized a circulating packed bed bioreactor for batch and continuous biodegradation studies.
• Assessed the degradation of trans-4-methyl-cyclohexane carboxylic acid (trans-4MCHCA) and cis-/trans-4-methyl-cyclohexane acetic acid (4-MCHAA).
• Analyzed the influence of carbon number and alkyl side branch arrangement on biodegradability.

Main Results:

• Biodegradability varied with naphthenic acid structure (carbon number and spatial arrangement).
• Achieved a maximum biodegradation rate of 209 mg/Lh for trans-4MCHCA in continuous operation, exceeding previous bioreactor reports.
• Observed significantly lower biodegradation rates for cis- and trans-4-MCHAA (4.2 and 7.8 mg/Lh, respectively).

Conclusions:

• The circulating packed bed bioreactor demonstrates high efficiency for naphthenic acid biodegradation.
• Naphthenic acid structure significantly impacts biodegradation rates, with trans-4MCHCA being more amenable to degradation.
• This bioremediation approach offers a viable solution for treating oil sands process water.