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Publication History View all

  • [show abstract] [hide abstract]
    ABSTRACT: The role of “homoionic” montmorillonites in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clay mineral used for this study was montmorillonite which was treated with the corresponding metal chloride salt to produce Na-, K-, Mg-, Ca-, Zn-, Al-, Cr-, and Fe-montmorillonites used in this study. The study indicated that Zn- and K-montmorillonites were inhibitory to biodegradation of the crude oil hydrocarbons and appears to do so as a result of extensive adsorption of the hydrocarbons. However, Na-, Ca- and Fe-montmorillonites with relatively high surface area and cation exchange capacity (CEC) were stimulatory to biodegradation of the crude oil hydrocarbons. This study reveals that whereas surface area and the ‘local bridging effect’ were important factors from the clay minerals that conferred stimulatory effect on the biodegradation of the hydrocarbons, the hydrolysis of the interlayer water by trivalent cations of the clay to generate protons and increase acidity of the medium is suggested to be inhibitory to biodegradation of the crude oil hydrocarbons. The interlayer cations (trivalent cations) that impart the highest local bridging effect which is stimulatory to biodegradation also impart the highest hydrolysis of interlayer water which is inhibitory. This study showed that interlayer cations play a crucial role on the ability of the clay mineral to influence biodegradation of the hydrocarbons.
    Applied Clay Science 01/2014; 87:81–86.
  • [show abstract] [hide abstract]
    ABSTRACT: The role of acid activated clays and unmodified clays in hydrocarbon removal during biodegradation was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The clay minerals used for this study were Na-montmorillonite, palygorskite, saponite and kaolinite. The clay mineral samples were treated with hydrochloric acid to produce acid activated clays which were used in this study. The study indicated that acid activated clays and untreated kaolinite were inhibitory to biodegradation of the hydrocarbons via different mechanisms whereas the untreated saponite was neutral to biodegradation of the hydrocarbons. However, untreated palygorskite and Na-montmorillonite were stimulatory to biodegradation and appears to do so as a result of the clays' ability to provide high surface area for the accumulation of microbes and nutrients such that the nutrients are within the ‘vicinity’ of the microbes. Adsorption of hydrocarbons was significant during biodegradation especially with unmodified palygorskite, where there was more than 40% removal of total petroleum hydrocarbons (TPH) by adsorption in the experimental microcosm containing 5:1 ratio (w/w) of clay to oil.
    International Biodeterioration & Biodegradation 01/2014; 88:185–191.
  • [show abstract] [hide abstract]
    ABSTRACT: The impact of modified montmorillonites on adsorption and biodegradation of crude oil C1-phenanthrenes, C1-dibenzothiophenes, C2-phenanthrenes and C2-dibenzothiophenes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. Consequently, the effect on C1-dibenzothiophenes/C1-phenanthrenes, C2-dibenzothiophenes/C2-phenanthrenes, 2+3-methyldibenzothiophene/4-methyldibenzothiophene and 1-methyldibenzothiophene/4-methyldibenzothiophene ratios commonly used as diagnostic ratios for oil forensic studies was evaluated. The clay mineral samples were treated to produce acid activated montmorillonite, organomontmorillonite and homoionic montmorillonite which were used in this study. The different clay minerals (modified and unmodified) showed varied degrees of biodegradation and adsorption of the C1-phenanthrenes, C1-dibenzothiophenes, C2-phenanthrenes and C2-dibenzothiophenes. The study indicated that as opposed to biodegradation, adsorption has no effect on the diagnostic ratios. Among the diagnostic ratios reviewed, only C2-dibenzothiophenes/C2-phenanthrenes ratio was neither affected by adsorption nor biodegradation making this ratio very useful in forensic studies of oil spills and oil-oil correlation.
    Biodegradation 11/2013;
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    ABSTRACT: A significant characteristic of the UK’s rapidly ageing population is the high percentage of older adults who rely extensively on their private automobile to stay mobile. There are, however, functional declines that occur with ageing that affect one’s ability to drive safely. Additionally, navigating becomes more difficult as we age and can result in older adults reducing the amount they drive on unfamiliar routes. Thus, understanding how older drivers currently plan and then way-find journeys will allow for future in-vehicle navigation systems to be more appropriate for the needs of older adults. The paper reports on the findings of six focus groups with older drivers; three groups with those who use in-vehicle navigation systems and three groups with those who do not. The focus groups found that the use of in-vehicle navigation systems provide older drivers with an increased confidence on the roads, companionship in the car and an element of pleasure in driving. When planning long distance trips, older drivers will use online planning tools that provide a familiarity with their traditional method of navigation the road atlas. Some participants who currently use no driving aids reported the use of potentially unsafe navigating behaviours to assist them on road network; indicating a clear need for assistance in navigating. Finally, there are some significant barriers for in-vehicle navigation systems to overcome before they can be considered beneficial for older drivers.
    Transportation Research Part F Traffic Psychology and Behaviour 11/2013; 21(1):173-180.
  • The ISME Journal 10/2013;
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    ABSTRACT: A simple "first generation" multi-scale computational model of the formation of activated sludge flocs at micro-scale and reactor performance at macro-scale is proposed. The model couples mass balances for substrates and biomass at reactor scale with an individual-based approach for the floc morphology, shape and micro-colony development. Among the novel model processes included are the group attachment/detachment of micro-flocs to the core structure and the clustering of nitrifiers. Simulation results qualitatively describe the formation of micro-colonies of ammonia and nitrite oxidizers and the extracellular polymeric substance produced by heterotrophic microorganisms, as typically observed in fluorescence in situ hybridization images. These results are the first step towards realistic multi-scale multispecies models of the activated sludge wastewater treatment systems and a generic modelling strategy that could be extended to other engineered biological systems.
    Water Research 10/2013;
  • Water Research 09/2013;
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    Applied and environmental microbiology 07/2013; 79(14):4515-4516.
  • [show abstract] [hide abstract]
    ABSTRACT: The effect of modified montmorillonites on the biodegradation and adsorption of selected steranes, diasteranes and hopanes was investigated in aqueous clay/oil microcosm experiments with a hydrocarbon degrading microorganism community. The unmodified montmorillonite was treated with didecyldimethylammonium bromide, hydrochloric acid and the relevant metallic chloride to produce organomontmorillonite, acid activated montmorillonite and homoionic montmorillonite respectively which were used in this study. The study indicated that organomontmorillonite, acid activated montmorillonite and potassium montmorillonite did not support the biodegradation of the selected steranes, diasteranes and hopanes as alteration of the biomarkers via biodegradation varied from a paltry 2-6 %. The adsorption of the selected biomarkers on acid activated montmorillonite and organomontmorillonite was also poor. However, adsorption of the biomarkers on potassium montmorillonite was relatively high. Sodium montmorillonite and unmodified montmorillonite appear to stimulate the biodegradation of the selected biomarkers moderately (30-35 %) with adsorption occurring at low level. Calcium montmorillonite and ferric montmorillonite effected significant biodegradation (51-60 %) of the selected biomarkers.
    Environmental Science and Pollution Research 06/2013;
  • [show abstract] [hide abstract]
    ABSTRACT: As part of a programme of finding new uses for industrial wastes, a trial of PFA (pulverized fuel ash) as a thermal grout for borehole heat exchangers has been tested experimentally. Several mixes of PFA-based grouts were developed by blending PFA with different solid materials by weight in different mix proportions with a constant percentage of cement. The materials used in these mixes are: fine sand, coarse sand, ground glass, and fluorspar. The thermal conductivity of seven different groups of grouts has been measured at dry and saturated conditions. A new thermal cell that utilizes the steady state technique developed by Newcastle University was used for these measurements. The results show poor enhancement of thermal conductivity using fine sand or medium ground glass, with maximum value of 1.15 W/m K at saturation. Results obtained using coarse or mixed ground glass gave a maximum value of 1.39 W/m K. The highest thermal conductivity values were achieved using fluorspar or coarse sand where the thermal conductivity reached 2.88 and 2.47 W/m K respectively at 20% of PFA. It was also observed that the combination of fluorspar with coarse ground glass can offer relatively high thermal conductivity at both dry and saturated conditions. Moreover, this combination of materials comprises a practical amount of low-cost material (PFA and ground glass).
    Applied Thermal Engineering 05/2013; 54(2):559–564.
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