Microbial-assisted extraction of bentonite from waste drilling fluid: A sustainable approach for waste management

Bentonite is an important component of water-based drilling mud, giving it important rheological properties. However, the drilling mud becomes contaminated with petroleum hydrocarbons when it comes to the surface from greater depths, making the bentonite unsuitable for reuse in drilling operations. As a result, polluted drilling mud is frequently disposed of in landfills without being treated. This paper presents an eco-friendly solution that does not require external energy, promotes sustainable reuse of drill fluids and materials, and is cost-effective to treat the contaminated bentonite so it can be used again in the drilling process. The primary aim of the study was to assess the capacity of naturally occurring microorganisms found at different depths within an oil well to degrade crude oil and extract bentonite that had been contaminated by petroleum hydrocarbons. For that, samples of waste drilling mud of 400, 800, 1200, 1600, and 1682 m depth were collected from one central PSU. Isolation and screening were done for all the depths, and one isolate from 1682m showed the highest degradation efficiency (64% at 7 days) by gravimetric analysis and was identified as Pseudomonas stutzeri based on nucleotide homology and phylogenetic analysis. This bacterial culture was used to extract bentonite from drilling mud in a 1:1 proportion, and the extracted bentonite was analysed using FT-IR. Also, a comparative study was conducted to assess the impact of hydrocarbon contamination on Atterberg's limits and specific gravity of the bentonite.