Ran Ding

Comparison of archaeal and bacterial community structures in heavily oil-contaminated and pristine soils

Archaeal and bacterial community structures in heavily oil-contaminated and pristine soils were compared using denaturing gradient gel electrophoresis and 16S rRNA gene libraries. The results showed that archaeal diversity was more complex in the contaminated soil than in the uncontaminated control soil. Archaeal populations in the contaminated soil consisted mainly of Euryarchaeota, with abundant methanogen-like operational taxonomic units (OTUs) and OTUs related to the phylogenetically diverse group, candidate division I, corresponding to rice cluster V. In contrast, only halophilic archaea were found in the pristine soil. Bacterial community structures also differed significantly between the contaminated and pristine soils. More clones from the contaminated soil were related to known hydrocarbon-degrading bacteria, implying that microorganisms with the potential to degrade petroleum were well-established. These results provide further insights into the composition of microbial communities in oil-contaminated soils.

Influence of ultrasonic waves on the removal of different oil components from oily sludge

Ultrasonic technology is a promising tool for washing oily sludge to recover oil. In this study, the influence of ultrasonic conditions on the removal of different oil components from oily sludge was investigated to optimize ultrasonic washing technology. Among the three frequencies (25, 50 and 100 kHz) applied, ultrasonic washing at 25 kHz exhibited the best performance in terms of oil extraction rate and efficiency. An ultrasonic intensity of 0.33 W/cm2 was necessary to overcome the energy threshold for oil washing. Application of a standing wave or dual frequencies did not improve the oil removal performance perceptibly. The optimum conditions for the removal of oil from oily sludge were an ultrasonic frequency of 25 kHz, intensity of 0.33 W/cm2 and sludge/water ratio of 1/2 (in volume). Thin-layer chromatographic flame ionization detection showed that ultrasonication could overcome high energy thresholds, resulting in an increase in the removal of asphaltenes and resins, with the removal of asphaltenes particularly affected by frequency. This study could provide valuable information for the application of ultrasonic technology in oily sludge treatment.

Treatment of 2-phenylamino-3-methyl-6-di-n-butylaminofluoran production effluent by combination of biological treatments and Fenton's oxidation

High strength refractory organic stream is produced during the production of 2-phenylamino-3-methyl-6-di-n-butylaminofluoran (One Dye Black 2, abbr. ODB 2), a novel heat-sensitive material with a promising market. In this study, a combination of acidification-precipitation, primary biological treatment, Fentons oxidation and another biological treatment was successfully used for the removal of COD from 18000-25000 mg/L to below 200 mg/L from the ODB 2 production wastewater in a pilot experiment. A COD removal of 70%-80% was achieved by acidification-precipitation under a pH of 2.5-3.0. The first step biodegradation permitted an average COD removal of 70% under an hydraulic residence time (HRT) of 30 h. By batch tests, the optimum conditions of Fentons oxidation were acquired as: Fe2+ dose 6.0 mmol/L; H202 dose 3000 mg/L; and reaction time 6 h. The second step biological treatment could ensure an effluent COD below 200 mg/L under an HRT of 10 h following the Fentons treatment.

Ultrasonic washing for oily sludge treatment in pilot scale

HighlightsUltrasonic washing conditions were optimized for oily sludge treatment in pilot scale.An ultrasonic power of 0.24 w/cm2 was necessary to overcome the energy threshold for oil washing at the frequency of 25 kHz.The oil removal rate could be 82–90% by ultrasound assistant with surfactants. ABSTRACT Ultrasonic technology is a promising tool for washing oily sludge to remove oil, however, little information has been provided on the pilot scale application of ultrasonic washing. In this study, the ultrasonic conditions were optimized based on the pilot trial of the effects of ultrasonic properties on oil removal from oily sludge. An ultrasonic power of 0.24 w/cm2 was necessary to overcome the energy threshold for oil washing at the frequency of 25 kHz. The removal rate was changed from 46.0% to 60.7% with oily sludge content from 25.0% to 42.0%, respectively. The addition of surfactants could improve oil recovery, and the optimizing content for sodium petroleum sulfonate and Span 80 was 0.3% and 0.03%, respectively. A series of pilot scale test indicated that the oil removal rate could be 82–90% by ultrasound assistant with surfactants (Span 80). Thin‐layer chromatographic flame ionization detection showed that the removal rate by ultrasonic wash was dropped with the increase of composition polarity. However, under the assistance of surfactants (Span 80), all compositions could be effectively removed. This pilot study will greatly improve the application of ultrasonic technology in oily sludge treatment.