This research has investigated the biodegradation of hydrocarbons particularly n-alkanes using open mixed culture which is relevant for both microbial enhanced oil recovery (MEOR) and the bioremediation of hydrocarbon contaminated soils. Biodegradation of n-C12, C14, C16, C18, C20 and some readily biodegradable substrates (glucose, acetic acid and ethanol) was studied using a respirometric method developed to assess the biodegradability of these compounds. Laboratory batch and semi-continuous experiments were performed in small-scale bioreactors at room temperature and 40oC under various conditions i.e. aerobic, anoxic with nitrate, sulfate reducing and completely anaerobic conditions using two different sources of open mixed microbial cultures obtained from an agricultural site and anaerobic digestion plant. Glucose, acetic acid, ethanol, C12, C14 and C16 were degraded microbially under aerobic batch conditions to nondetectable levels at room temperature and 40oC using the two sources of inoculum whereas C18 and C20 were degraded partially under room temperature and to nondetectable levels at 40oC with the two inocula sources. Under aerobic semi-continuous, glucose and the n-alkane substrate were biodegraded even at low hydraulic retention time (HRT). Under anaerobic conditions, the n-alkanes were utilized by the soil inoculum at room temperature and at 40oC with nitrate as the electron acceptor but no microbial activity was observed under sulfate reducing and completely anaerobic conditions. The open mixed cultures require an initial acclimation period before utilizing the substrates. The acclimation period was significantly shorter under aerobic conditions than anaerobic conditions for the n-alkanes. Acclimation periods of approximately 1-2 days under aerobic conditions was observed for the readily biodegradable substrates and 2 days for glucose under anoxic conditions. The acclimation periods for the nalkanes was between 3-5 days under aerobic conditions and approximately 2 weeks under anoxic conditions. The acclimation period was not affected by the substrate concentration and inoculum type however, for the n-alkanes, the acclimation period was reduced by 1-2days under aerobic conditions at 40oC. The biodegradation of the liquid hydrocarbons was more significant than the solids at room temperature but in general higher temperature increased the degree of biodegradation. The electron acceptor consumption data i.e. dissolved oxygen and nitrate consumption data obtained was mathematically modelled using Monod kinetics to obtain biokinetic parameters. Good fittings between the model solution and the experimental data was obtained. The biokinetic parameters obtained were within the range of values reported in literature. The use of respirometric data for the estimation of biodegradation kinetic parameters can be very reliable. The consistency of the data obtained show that the approach is very reproducible and quality information can be obtained. The results of this study showed that the open mixed microbial cultures from soil and AD inocula contained diverse microorganisms capable of utilizing both liquid and solid n-alkanes at room temperature and 40oC under aerobic and anoxic conditions.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:715471 |
| Date | January 2017 |
| Creators | Uzukwu, Chukwuemeka |
| Publisher | University of Aberdeen |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=231857 |
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