Aerobic Degradation of Drill Muds by Axenic and Mixed Bacterial Isolates from Drill Cuttings at Ologbo, Edo State, Nigeria

Abstract

Increasing exploration and production activities, coupled with improper waste disposal practices have encouraged widespread contamination of ecological systems at locations of these activities. This study was to examine the biodegradation potentials of axenic and mixed bacterial isolates associated with drill cuttings emanating from onshore well located at Ologbo, Edo State. Aerobic biodegradation was determined using screen test and shake flask experiment (assessing the total viable counts (cfu/ml), pH, turbidity, Biological Oxygen Demand (BOD₅) and Chemical Oxygen Demand (COD) for a period of 28 days. Results revealed heavy growth in broth cultures amended with glucose and drill muds. In shake flask experiment, the highest total viable counts of 10.2 x 103cfu/ ml and 6.4 x 10³ cfu/ ml were recorded for cultures containing consortium of isolates (Enterobacter aerogenes + Micrococcus sp. In water based mud (WBM) broth; Enterobacter aerogenes + Micrococcus sp. in synthetic based mud (SBM) broth. The COD (reduced from 65 mg/ l at day 1 to 47 mg/ l at day 28) and BOD5 (reduced from 22.2 mg/ l at day 1 to 0.7 mg/ l at day 28 in synthetic based mud) results are evidence of the oxidation of the substrates. There was no significant difference in the degradation of the drilling muds by the isolates (p > 0.05). It was therefore shown that these selected isolates have potential applications in the bioremediation of sites polluted with muds waste.

Keywords: Onshore drill-cutting, drill muds, microorganisms, biodegradation

Nig J. Biotech. Vol. 25 (2013) 46-52