Enhanced Biodegradation of Oil Based Drilling Fluids in Bonny River, Nigeria

Abstract

Drilling fluids, also referred to as drilling muds, play a crucial role in rotary drilling operations by lubricating and cooling the drill bit during oil and gas exploration both onshore and offshore. However, the discharge of these fluids, particularly oil-based drilling fluids (OBF), into marine ecosystems poses significant environmental risks, including the degradation of water quality and harm to aquatic organisms. This study investigated the enhanced biodegradation of OBF in marine water (MW) through bioaugmentation with Pseudomonas aeruginosa strain EB38 and Bacillus safensis strain UIS0051, alongside biostimulation using fish waste (FW) as a nutrient source. Biodegradation efficiency was assessed by monitoring the percentage reduction in Total Hydrocarbon Content (THC) over a 28-day period. A Randomized Complete Block Design (RCBD) was employed, comprising eight experimental setups with a final volume of 1000 mL each. Following contamination with OBF, microbial inoculants and fish waste were introduced to the treatment setups. Both physicochemical and microbiological parameters were measured before and after contamination using standard procedures. The initial THC concentration in the contaminated marine water (MW + OBF) was 3,736.0 mg/L. After 28 days, the percentage reduction in THC across the different treatments, in descending order of efficiency, was: MW + OBF + Pseudomonas (98.79%) > MW + OBF + Bacillus (98.60%) > MW + OBF + FW + Pseudomonas (97.86%) > MW + OBF + FW + Bacillus (97.75%) > MW + OBF + FW + Pseudomonas + Bacillus (97.54%) > MW + OBF + FW (95.06%). In conclusion, Pseudomonas aeruginosa strain EB38 demonstrated superior efficacy in degrading oil-based drilling fluids in marine water compared to Bacillus safensis strain UIS0051. The findings indicate that bioaugmentation with selected microbial strains and biostimulation using organic waste such as fish waste can significantly enhance the biodegradation of hydrocarbons in marine environments. This approach represents a promising, eco-friendly, and cost-effective strategy for the bioremediation of drilling-related pollutants and promotes sustainable practices in oil and gas exploration.