Multi-Tiered Analytical Approach for Assessing Produced Water Contaminants and Environmental Risks

Produced water (PW) is the largest waste stream generated during oil and gas production and poses significant environmental challenges, particularly in water-scarce regions. This study presents a multi-tiered assessment of PW from six Libyan oilfields across three sedimentary basins, integrating physicochemical characterization, trace metal and lithium analysis, radiological evaluation, and molecular identification of selected cultured bacterial isolates. Results revealed substantial variability, with total dissolved solids ranging from 8443 to 222,000 mg/L, chloride up to 153,423 mg/L, and total petroleum hydrocarbons reaching 98.5 mg/L. Elevated concentrations of barium, strontium, iron, and mercury exceeded guideline limits in selected samples. Radiological analysis indicated low radionuclide activity in the aqueous phase, while scanning electron microscopy confirmed NORM accumulation in sulfate-rich mineral scales. Molecular identification using 16S rRNA sequencing revealed hydrocarbon-degrading bacteria, including Microbacterium ureisolvens, Exiguobacterium aquaticum, Kocuria rosea, and Nocardia coubleae, with the latter two, to the best of our knowledge, reported for the first time in PW environments. These findings provide insight into selected cultured bacterial isolates associated with PW and their potential relevance for bioremediation. Overall, the results provide a baseline understanding of PW characteristics in the analyzed samples and emphasize the need for further large-scale investigations.