Co-composting of Non-aqueous Drilling Fluid Contaminated Cuttings from Ologbo Active Oilfield with Organic Manure

Abstract

Drill cuttings (from Ologbo active oil field) contaminated with non-aqueous drilling fluid was co-composted with poultry manure and plant waste for eighteen weeks. A homogenized non-aqueous based fluid contaminated cutting was mixed with wood chips in a ratio of 1:1 and then mixed with soil, poultry and plant waste manure in ratio of 4:2:1. Results of total heterotrophic bacterial counts showed steady increase in counts from week 0 to week 12 in all treatments. The highest bacterial count of 8.8 x 10⁷ ± 0.2 cfu/g was observed in macrocosm containing drill cuttings, soil and poultry manure at week 12. The highest fungal count of 6.5 x 10⁴ ±0.2 cfu/g occurred in macrocosm containing drill cuttings, soil and poultry manure at week 12. The mixed community population of the compost system was observed to compose of ten (10) bacterial genera and five (5) fungal genera. The highest recorded pH was 8.15. Steady decreases were observed in electrical conductivity of the compost systems. Macrocosms containing poultry manure and plant waste had the highest percentage reduction of oil and grease and total petroleum hydrocarbon (99.57% and 99.92% respectively). Based on the findings from this study it is recommended that oil exploration and production companies should adopt compost technology with organic manure such as poultry and plant waste manure, as a waste management policy in order to reduce the high cost, energy and pollution associated with other conventional treatment options.

Keywords: drill-cuttings, non-aqueous based fluid, bacteria, fungi, TPH