The Kinetics of Biodegradation of Trans-4-Methyl-1-Cyclohexane Carboxylic Acid
In batch reactors, the maximum specific growth rate (0.52±0.04 d-1) of the consortium at 23oC and neutral pH was not highly variable over various initial substrate concentrations (50 to 750 mg/L). Batch experiments indicated that biodegradation can be achieved at low temperatures; however, the biodegradation rate at 4oC was only 22% of that at room temperature (23oC). Biodegradation at various pH values indicated a maximum specific growth rate of 1.69±0.40 d-1 and yield (0.41±0.06 mg/mg) at a pH of 10.
Study of the candidate substrate using a continuously stirred tank reactor and the microbial culture developed in the batch experimentations revealed that the kinetics of the candidate naphthenic acid are best described by the Monod expression with a maximum specific growth rate of 1.74±0.004 d-1 and a half saturation constant of 363±17 mg/L. The continuously stirred tank reactor achieved a maximum reaction rate of 230 mg/(L?d) at a residence time of 1.6 d-1 (39 h).
Two high porosity immobilized cell reactors operating continuously over three months were found to consume trans-4MCHCA at a rate almost two orders of magnitude higher than a continuously stirred tank reactor. The immobilized cell systems attained a maximum reaction rate of 22,000 mg/(L?d) at a residence time of 16 minutes. High porosity immobilized cell reactors were shown to effectively remove a single naphthenic acid substrate in continuously fed operation to dilution rates of 90 d-1. A plug flow model best represented the degradation in the immobilized cell systems and was demonstrated to be a useful tool for studying the effects of parameter variation and prediction of reactor performance. This work highlights the potential of augmented bioremediation systems for the degradation of naphthenic acids.
Advisor:Mehrotra, Anil; Soltan, Jafar; Dube, Monique; Niu, Catherine; Maule, Charles; Headley, John V.; Nemati, Mehdi; Hill, Gordon A.
School:University of Saskatchewan
School Location:Canada - Saskatchewan
Source Type:Master's Thesis
Keywords:kinetics bioreactors naphthenic acids 4 methyl 1 cyclohexane carboxylic acid
Date of Publication:07/15/2008