Enhanced methane production and hydrocarbon removal from petroleum refinery sludge after Pseudomonas putida pretreatment and process scale-up.

The influence of Pseudomonas putida 7525 strain on the pretreatment of petroleum refinery sludge was optimized at different dosages to maximize solubilization for improved biodegradability. Laccase-producing P. putida strain at a dosage of 10 CFU/mL resulted in 249% and 121.57% increments in soluble chemical oxygen demand and volatile fatty acids production respectively as compared to untreated within 6 days of incubation. 1L biochemical methane potential test conducted for optimization of different inoculum and pretreated substrate ratios (0.3, 0.4, 0.5, 0.7 and 1.0) revealed maximum methane augmentation (62%) and volatile solids degradation (66.7%) at ratio 0.5. Scaled-up study (20L) for ratio 0.5 resulted in 57.07% total petroleum hydrocarbon, 62.98% oil and grease and 91.9% phenol removal within 50 days of digestion of pretreated PS. Kinetic modelling of cumulative methane yield indicated that modified Gompertz model showed the best fit thereby, evincing the potency of bacterial species for bioremediation of PS.