Total Nitrogen and Bacterial Analysis in Oil-Based Drill Cuttings Contaminated Soils Planted with Grass Species

Abstract

The possibility of grass species phytoremediating oil-based drill cuttings contaminated soils was examined by assessing changes in bacterial load, bacterial species, and soil nitrogen. The experiment was modelled in a randomized complete block design by factorial of 6 x 3 x 2 x 2 for grass species, drill cuttings, time, and growth stage. The parameters assessed were total nitrogen, nitrogen reduction, bacterial load, and bacterial load reduction in soils. There was significant decrease in nitrogen from day of planting to harvesting. The highest reduction was observed in 0% and 25% treatments in mature P. maximum and young C. virgata. The lowest reduction was seen in A. compressus at 50% treatment. Significant difference in bacterial load was noticed in time in each treatment. Highest reduction of bacterial load was seen in 0% treatment level planted with A. compressus, A. gayanus, young C. virgata, H. contortus, P. maximum, and unplanted soils, which were not significantly different from 25% and 50% oil-based drill cuttings treatment except in young H. contortus and P. maximum. The lowest reduction was observed in 25% treatment level of young H. contortus and P. maximum. Micrococcus sp, Bacillus sp., and Staphyloccocus aureus were found in soils of the three treatment levels at planting.  In addition, Protus sp was seen in soils of 0% and 50% treatment levels. Erwinnia sp and Escherichia coli was identified in 25% and 50% oil-based drill cuttings treated soils. Klebsiella sp was isolated from 25% oil-based drill cuttings treated soils. Therefore, Erwinia sp, E. coli, and Klebsiella sp were associated with oil-based drill cuttings contamination.