Rapid effective treatment of waxy oily sludge using a method of dispersion combined with biodegradation in a semi-fluid state

Functional and structural responses of a halophilic consortium to oily sludge during biodegradation

Biotreatment of oily sludge and the involved microbial communities, particularly in saline environments, have been rarely investigated. We enriched a halophilic bacterial consortium (OS-100) from petroleum refining oily sludge, which degraded almost 86% of the aliphatic hydrocarbon (C10-C30) fraction of the oily sludge within 7 days in the presence of 100 g/L NaCl. Two halophilic hydrocarbon-degrading bacteria related to the genera Chromohalobacter and Halomonas were isolated from the OS-100 consortium. Hydrocarbon degradation by the OS-100 consortium was relatively higher compared to the isolated bacteria, indicating potential synergistic interactions among the OS-100 community members. Exclusion of FeCl2, MgCl2, CaCl2, trace elements, and vitamins from the culture medium did not significantly affect the hydrocarbon degradation efficiency of the OS-100 consortium. To the contrary, hydrocarbon biodegradation dropped from 94.1 to 54.4% and 5% when the OS-100 consortium was deprived from phosphate and nitrogen sources in the culture medium, respectively. Quantitative PCR revealed that alkB gene expression increased up to the 3rd day of incubation with 11.277-fold, consistent with the observed increments in hydrocarbon degradation. Illumina-MiSeq sequencing of 16 S rRNA gene fragments revealed that the OS-100 consortium was mainly composed of the genera Halomonas, Idiomarina, Alcanivorax and Chromohalobacter. This community structure changed depending on the culturing conditions. However, remarkable changes in the community structure were not always associated with remarkable shifts in the hydrocarbonoclastic activity and vice versa. The results show that probably synergistic interactions between community members and different subpopulations of the OS-100 consortium contributed to salinity tolerance and hydrocarbon degradation.

Performance evaluation of rhamnolipid biosurfactant produced by Pseudomonas aeruginosa and its effect on marine oil-spill remediation

This study aimed to reveal that the effect of biosurfactant on the dispersion and degradation of crude oil. Whole genome analysis showed that Pseudomonas aeruginosa GB-3 contained abundant genes involved in biosurfactant synthesis and metabolic processes and had the potential to degrade oil. The biosurfactant produced by strain GB-3 was screened by various methods. The results showed that the surface tension reduction activity was 28.6 mN·m-1 and emulsification stability was exhibited at different pH, salinity and temperature. The biosurfactant was identified as rhamnolipid by LC-MS and FTIR. The fermentation conditions of strain GB-3 were optimized by response surface methodology, finally the optimal system (carbon source: glucose, nitrogen source: ammonium sulfate, C/N ratio:16:1, pH: 7, temperature: 30-35 °C) was determined. Compared with the initial fermentation, the yield of biosurfactant increased by 4.4 times after optimization. In addition, rhamnolipid biosurfactant as a dispersant could make the dispersion of crude oil reach 38% within seven days, which enhanced the bioavailability of crude oil. As a biostimulant, it could also improve the activity of indigenous microorganism and increase the degradation rate of crude oil by 10-15%. This study suggested that rhamnolipid biosurfactant had application prospect in bioremediation of marine oil-spill.

Hydrogen-rich gas production via supercritical water gasification (SCWG) of oily sludge over waste tire-derived activated carbon impregnated with Ni: Characterization and optimization of activated carbon production

In this study, the production of activated carbon (AC) through the chemical activation of waste tire (WT) using H3PO4 and KOH for H2 production by SCWG of oily sludge (OS) donated by Persian Gulf Star Oil Company was investigated. H3PO4 was the best activating agent based on some pretests results, and then the synthesis of AC was optimized using Response Surface Methodology. Based on BET surface area of synthesized ACs, thirty combinations of the four variables namely; activation temperature (350-550 °C); activation time (1-4 h); H3PO4 to WT ratio (1-3 w.w-1); and H3PO4 concentration (20-40 wt%) were optimized. CHNS, TGA, FE-SEM, and EDS-mapping analyses were used to characterize the AC and catalyst synthesized in optimum condition (activation temperature: 450 °C; activation time: 2.5 h; H3PO4 to WT ratio: 2 w.w-1; and H3PO4 concentration: 40 wt%), which presented a surface area of 170 m2 g-1. Finally, Ni was impregnated on the optimized AC with different loadings (5-15 wt%) to evaluate its performance in H2 production by SCWG of OS. Although H2 yield in catalytic experiments was higher than that observed in non-catalytic experiment, results showed that the maximum H2 selectivity was 66% in SCWG of OS using AC impregnated with 10 wt% Ni.