Rhizobacterial-assisted phytoremediation for accelerated petroleum-hydrocarbon removal in crude-oil sludge

Almost over ten years, environmental experts have concentrated on implementing risk-based management strategies for the remediation of sites contaminated with total petroleum hydrocarbons (TPHs), which can potentially have detrimental ecological impacts. Phytoremediation widely recognized as a green technology a plant-based and economically efficient technology, emerges as a promising method to offer an alternative to existing treatment technologies in TPH contaminated ecosystems. The utilization of Scirpus grossus, a perennial plant, has been proposed as a practical, safe, and cost-effective method for remediating soil contaminated with petroleum hydrocarbons. This study aimed to evaluate the efficacy of S. grossus in removing total petroleum hydrocarbons (TPH) in real crude-oil sludge. Employing a batch phytoremediation system with S. grossus, the experiment was conducted in crates within a greenhouse, maintaining ambient temperatures (30 °C-35 °C) for a duration of 28 days. Each crate was populated with 9-month-old plants of uniform size, initially cultivated in the greenhouse before being transplanted into crates containing 100 % crude-oil sludge with an initial TPH concentration of 37,554 mg/kg for the treatment phase. TPH removal rates were assessed after 14, 21, and 28 days of exposure, resulting in removal rates of 67 %, 74 %, and 75 %, respectively. The highest concentration of rhizobacteria recorded in both sample (with contaminants and without contaminants) were 5.56 × 104 and 5.72 × 104 CFU/mL respectively. Furthermore, TPH extraction from both stems and roots of S. grossus was analysed, revealing the highest TPH concentration of 15,319 mg/kg and about 8000 mg/kg of TPH at day 28 by roots and stem sample respectively. In conclusion, S. grossus demonstrated substantial potential in effectively mitigating the toxicity of TPH in real crude-oil sludge contamination scenarios.