Enhancing natural attenuation for oil-contaminated soils using a combination of low-carbon bioengineered approaches.
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This thesis presents an extensive study aimed at optimising natural attenuation for oil- contaminated soils by employing a combination of low-carbon bioremediation strategies. Responding to the urgent need for sustainable remediation practices, this work systematically evaluates the efficiency of bioremediation techniques, focusing on their potential implementation in the Niger Delta, a region severely impacted by oil contamination. An initial review identified bioremediation and bioadmendment with compost or biochar as effective low-carbon strategies, tailored to the unique conditions of the Niger Delta. An elaborate laboratory investigation of diverse biostimulation strategies subsequently confirmed the superior efficiency of combined treatments over singular approaches. Notably, integrating oxygen-release compounds (ORC) with food waste compost significantly enhanced microbial activities, accelerating the degradation of total petroleum hydrocarbons (TPH). Further exploration revealed the benefits of bioaugmentation with biochar for managing recurring spills. The combination of wheat straw biochar and specific bacterial strains resulted in markedly higher remediation efficiency in recurrently contaminated soil, underscoring the crucial role and adaptability of microbial communities in such scenarios. To streamline decision-making processes, a decision tree framework based on the Analytical Hierarchy Process (AHP) was developed. This tool assesses the techno-economic and sustainability aspects of the proposed remediation strategies. The decision tool highlights that the use of ORC with compost, and wheat straw biochar augmented with Pseudomonas aeruginosa and Bacillus sonorensis holds substantial promise. However, it underscores the importance of comprehensive site assessments, drawing attention to potential constraints in diverse environmental contexts. This research offers novel insights into refining bioremediation techniques and paves the way for future advancements in this critical field. The findings could guide the development of more efficacious, sustainable, and cost-effective remediation strategies for oil- contaminated soils, with continued refinement and application anticipated.