Treatment of petroleum refinery sludge by petroleum degrading bacterium Stenotrophomonas pavanii IRB19 as an efficient novel technology

Simultaneous bioremediation of diesel-contaminated soil and water ecosystems using mixed culture of Acinetobacter baumannii IITG19 and Providencia vermicola IITG20

Diesel degradation and bacterial growth were investigated in soil, marine water, and freshwater ecosystems using Acinetobacter baumannii IITG19, Providencia vermicola IITG20, and their mixed culture. Both bacteria were found to be effective in all three ecosystems, with the best degradation occurring in freshwater. Acinetobacter baumannii IITG19 showed higher degradation (59%, 62%, and 76%) than Providencia vermicola IITG20 (31%, 57%, and 67%) in soil, marine water, and freshwater, respectively. Alkanes showed higher degradation than naphthenes and aromatics for both strains. The mixed culture showed higher diesel degradation efficiency than individual strains in all ecosystems. The overall degradation was similar in soil and marine water (66%), while freshwater showed the highest degradation of 81%. In the presence of the mixed culture, the degradation of alkanes was more than 90%. Bacterial growth was highest in freshwater and lowest in soil for both bacteria and the mixed culture. Metabolite analysis confirmed alcoholic degradation for alkanes and cyclo-alcoholic degradation for naphthenes. The degradation rate for mixed culture was higher than that of both the individual strains. The mixed culture had highest degradation rate constant in freshwater at 0.11 day-1 followed by that in marine ecosystem at 0.078 day-1. The rate constant was lowest for soil ecosystem at 0.066 day-1. Thus the mixed culture showed effectiveness in all three ecosystems, with its highest effectiveness observed in the freshwater ecosystem.

Biodegradation of Petroleum Sludge by Methylobacterium sp. Strain ZASH

A bacterium was isolated from sludge-contaminated soil in a petroleum refinery and tested for its ability to degrade aliphatic hydrocarbon compounds present in petroleum sludge. The isolate was grown on minimal salt media agar supplemented with 1% (w/v) petroleum sludge. The isolate was tentatively identified as Methylobacterium s p. s t rain ZASH based on the partial 16s rDNA molecular phylogeny. The bacterium grew optimally between the temperatures of 30°C and 35°C, pH 7 and 7.5, 0.5% and 1.5% (v/v) Tween 80 as the surfactant, and between 1% and 2% (w/v) peptone as the nitrogen source. The constants derived from the Haldane equation were μmax = 0.039 hr-1, Ks = 0.385% (w/v) total petroleum hydrocarbons (TPH) or 3,850 mg/L TPH, and Ki =1.12% (w/v) TPH or 11,200 mg/L. The maximum biodegradation rate exhibited by this strain was 19 mg/L/hr at an initial TPH concentration of 10,000 mg/L. Gas chromatography analysis revealed that after 15 days the strain was able to degrade all aliphatic n-alkanes investigated with different efficiencies. Shorter n-alkanes were generally degraded more rapidly than longer n-alkanes with 90% removal for C-12 compared to only 30% removal for C-36. The addition of sawdust did not improve bacterial degradation of petroleum hydrocarbons, but it assisted in the removal of remaining undegraded hydrocarbons through adsorption.

Biotreatment of oily sludge by a bacterial consortium: Effect of bioprocess conditions on biodegradation efficiency and bacterial community structure

We studied the biodegradation of oily sludge generated by a petroleum plant in Bahrain by a bacterial consortium (termed as AK6) under different bioprocess conditions. Biodegradation of petroleum hydrocarbons in oily sludge (C₁₁-C₂₉) increased from 24% after two days to 99% after 9 days of incubation in cultures containing 5% (w/v) of oily sludge at 40°C. When the nitrogen source was excluded from the batch cultures, hydrocarbon biodegradation dropped to 45% within 7 days. The hydrocarbon biodegradation decreased also by increasing the salinity to 3% and the temperature above 40°C. AK6 tolerated up to 50% (w/v) oily sludge and degraded 60% of the dichloromethane-extractable oil fraction. Illumina-MiSeq analyses revealed that the AK6 consortium was mainly composed of Gammaproteobacteria (ca. 98% of total sequences), with most sequences belonging to Klebsiella (77.6% of total sequences), Enterobacter (16.7%) and Salmonella (5%). Prominent shifts in the bacterial composition of the consortium were observed when the temperature and initial sludge concentration increased, and the nitrogen source was excluded, favoring sequences belonging to Pseudomonas and Stenotrophomonas. The AK6 consortium is endowed with a strong oily sludge tolerance and biodegradation capability under different bioprocess conditions, where Pseudomonas spp. appear to be crucial for hydrocarbon biodegradation.

Enhanced biodegradation of total petroleum hydrocarbons by implementing a novel two-step bioaugmentation strategy using indigenous bacterial consortium

In the present study, a two-step bioaugmentation strategy (TSBS) was implemented by using indigenous bacterial consortium to enhance the degradation of total petroleum hydrocarbons (TPH) from petroleum refinery sludge (PRS). A bacterial consortium was developed using four indigenous isolated strains, Dietzia sp. IRB191, Dietzia sp. IRB192, Staphylococcus sp. BSM19 and Stenotrophomonas sp. IRB19 from PRS. The optimum conditions of pH, temperature, and sludge concentration were 7, 34 °C, and 2% (w/v), respectively, for maximum TPH degradation, obtained using one variable at a time approach. Under the optimal culture conditions, the developed consortium was inoculated twice to the culturing medium, at the beginning (0^th day) and again on the 10th day for implementing a novel TSBS. The maximum TPH degradation of 91.5 ± 2.28% was found with TSBS, which was 1.18 times higher than that of SSBS (77.3 ± 2.6%) in 15 days of incubation. GC-FID study also confirmed that the TPH present in the PRS was effectively degraded by the bacterial consortium with TSBS. The TPH degradation by using TSBS proceeded according to the first-order kinetics with a rate constant of 0.155 d^-1. Hence, biodegradation using a TSBS can be considered an effective and eco-friendly process for safe disposal of petroleum refinery sludge.