Enhanced phytoremediation of crude oil-contaminated soil using Cynodon dactylon with nutrient and mixed liquid suspended solids amendments

Phytoremediation of crude oil-contaminated soil requires strategies to overcome plant stress and enhance microbial degradation. This study evaluated an integrated approach using Bermuda grass (Cynodon dactylon) augmented with nutrients and a microbial consortium (MLSS). A 90-day pot experiment was conducted with soil contaminated with Bangistan crude oil (0.25–5% w/w). Treatments included unplanted control, planted control, and planted systems amended with NPK fertilizer and/or MLSS. The combined nutrient and MLSS amendment synergistically enhanced remediation. It achieved > 95% Total Petroleum Hydrocarbon (TPH) removal at the lowest concentration (0.25%), significantly increased rhizosphere microbial populations (~ 3 orders of magnitude), and improved plant biomass. First-order kinetics revealed a drastic reduction in TPH half-life from 296 days (unplanted) to 20 days in the optimized treatment. Efficiency decreased with increasing crude oil concentration, indicating a phytotoxicity threshold. The core innovation of this study is the demonstrated synergy between C. dactylon and an engineered rhizosphere microbiome through combined bioaugmentation and biostimulation. This strategy offers a highly effective, scalable, and sustainable protocol for rehabilitating oil-contaminated soils.