Oil Shale Solid Waste Research Articles

Impact of phytoremediation and bioaugmentation on microbial community in oil shale chemical industry solid waste

Field and laboratory experiments were carried out in order to estimate the suitability ofphytoremediation and bioaugmentation for oil shale chemical industry solid waste (semicoke) dump area remediation as well as influence of plants and laboratory selecteddegradative bacterial strains on the microbial communities in semi-coke, Field test plots (each50 m2) were established at semi-coke depository in July 200 I and samples for microbiologicaland chemical analysis were collected in October 2002 and 2003, Microbial communities insemi-coke were · analysed using both culture-based and molecular methods, Changes inmicrobial community structure and activity occurred in semi-coke as a result ofphytoremediation and bioaugmentation, Phytoremediation increased the number of oildegrading bacteria and diversity of microbial community in semi-coke as well as microbialbiomass. A comparison of 16S rRNA gene-based DGGE fingerprints of semi-coke samplesusing multivariate analysis showed variation between the bacterial community profiles fromdifferent treatments. Degradation rates of pollutants did not differ significantly between plotswith vegetation except for sod, showing negligible effect of soil amendment typeonbiodegradation activity. Our results indicate that increased biodegradation activity was due toproliferation of specific microbial groups, changes in taxonomic and metabolic diversity ofbacterial community and shifts in the structure of catabolic genes, Based on our findings weconclude that phytoremediation and bioaugmentation could be considered as an alternativemanagement option for remediation of oil shale solid waste.

TEMPORAL DYNAMICS OF MICROBIAL COMMUNITY IN SOIL DURING PHYTOREMEDIATION FIELD EXPERIMENT

Oil‐shale chemical industry creates approximately 600 000 tons of thermally processed oil shale solid wastes (semi‐coke) every year in Estonia. A field phytoremediation and bioaugmentation experiment has been monitored for three years in the solid waste depository area of oil‐shale chemical industry. We found enhanced degradation rates of pollutants in plots with vegetation and added bacterial biomass. The concentration of volatile phenols had decreased almost by 100 %, and the concentration of oil products had decreased approximately 3 times in planted plots compared to the control plots. The degradation rates were the highest in the upper soil layer which has the highest root density. Vegetation also changed the microbial community structure in comparison with the control plots. In addition to the vegetation, properties of the substrate had an essential effect on the microbial community.

Oil shale solid waste recycling in the development of new silica fillers for elastomeric composites

AbstractThe production of Brazilian shale oil gives rise to 6600 ton/day of a solid waste of retorted shale, and larger amounts of dolomitic waste rock are generated during mining. Two vitreous materials were obtained through the melting of different proportions of these two wastes. By leaching these materials with hydrochloric acid at 90°C, two different kinds of silicas (powder and gel, both amorphous) with specific surface areas reaching up to ∼ 420 m2/g were generated. These silicas were further modified through an Ostwald‐ripening type of treatment in ammonium hydroxide solution at 80°C. The process eliminated almost completely the deleterious micropores. The obtained silicas were evaluated as reinforcing fillers for SBR‐1502. The employment of one of the modified silicas gave rise to a composite with better mechanical properties than those displayed by the one with untreated silica. Scanning electronic microscopic observation disclosed the existence of great morphological differences between these silicas. Apparently, the aging treatment gave rise to the production of better anchoring sites for the elastomer molecules. NMR studies also showed the reduction of the silanol content of the treated silica. The fracture surface of the composite disclosed a good wetting of this silica by the elastomeric matrix. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2856–2867, 2001

Geochemical modeling to predict the chemistry of leachates from alkaline solid wastes: oil shale deposits, western U.S.A.

Abstract Oil shale processing at elevated temperatures to extract oil results in large amounts of alkaline oil shale solid wastes (OSSW). The objective of this study was to use a geochemical model to help predict the chemistry of leachates, including toxic chemicals, from OSSW. Several geochemical models were evaluated (e.g. EQ3/EQ6, GEOCHEM, MINTEQA2, PHREEQE, SOLMINEQ, WATEQFC); the model GEOCHEM was selected based on its more comprehensive capabilities. The OSSW samples were subjected to solubility and XRD studies. Element concentrations and pH of OSSW leachates were used as input to GEOCHEM to predict their chemistry. Ion activity products were used to infer the likely solid phases controlling the concentration of toxic elements (e.g. F and Mo) in these leachates. The model predicted that silicate phases produced during the heating process buffered the pH and controlled concentrations of major cations. The F concentrations in OSSW leachates appeared to be controlled by fluorite (CaF 2 ). Contrary to previous findings, powellite (CaMoO 4 ) probably does not control the concentrations of Mo in OSSW leachates.

Time domain reflectometry for measuring volumetric water content in processed oil shale waste

Time domain reflectometry (TDR) was evaluated and developed to monitor volumetric water content (θυ) in oil shale solid waste retorted and combusted by the Lurgi‐Ruhrgas process. A TDR probe was designed and tested that could be buried and compacted in waste embankments and provide in situ measurements for θυ in the high‐saline and high‐alkaline conditions exhibited by this waste. TDR was found to be accurate for measurement of θυ across a broad range of water contents in the processed oil shale waste. A computer algorithm to automate the analysis of TDR traces to determine θυ, was developed and tested. A sensitivity test was performed to analyze differences between three smoothing algorithms on the measurement. No significant differences were found between smoothing algorithms or between the number of points applied for smoothing.

Effects of a carbon dioxide pressure process on the solubilities of major and trace elements in oil shale solid wastes

Processing of oil shale at high temperatures produces a highly alkaline solid waste. The waste can be stabilized by a recarbonation process. In order to test a method for accelerating the recarbonation process, the authors exposed three moist oil shale solid waste (OSSW) samples to 5 psi CO{sub 2} pressure for 1 h. The treated and untreated samples were equilibrium with water for 7 days and the chemical composition of the aqueous extracts determined. Before CO{sub 2} treatment, the Ca{sup 2+} and Mg{sup 2+} concentrations appeared to be controlled by silicate phases present in the waste such as wollastonite (CaSiO{sub 3}), forsterite (Mg{sub 2}SiO{sub 4}), and talc (Mg{sub 3}Si{sub 4}O{sub 10}(OH){sub 2}), which buffered the pH at {approximately}12.0. The Co{sub 2} treatment lowered the pH from 12.0 to {approximately}9.0 through the formation of calcite. The Ca{sup 2+} concentrations from Co{sub 2}-treated samples suggested a close approach to saturation with respect to calcite (CaCO{sub 3}) whereas the Mg{sup 2+} concentrations appeared to be controlled by either magnesite (MgCO{sub 3}) or possibly a silicate. The CO{sub 2} treatment generally decreased F and Mo concentrations in aqueous extracts. The F{sup {minus}} concentration before and after Co{sub 2} treatment appeared to be controlled bymore » fluorite (CaF{sub 2}). Results demonstrate that the CO{sub 2} pressure process is an effective means of reducing the pH and the concentrations of F and Mo in aqueous extracts from alkaline solid wastes.« less

Solubility and release of fluorine and molybdenum from oil shale solid wastes

Surface disposal of oil shale solid wastes may contaminate surface water and ground-water resources with toxic levels of fluorine (F) and molybdenum (Mo). Three different oil shale solid wastes produced from processing raw oil shale, at different temperatures, were subjected to equilibrium solubility studies to examine the solid phases responsible for the release of F and Mo from oil shale solid wastes into the infiltrating water. The results suggested that increased retorting temperatures increased pH from 10.75 to 12.35, decreased dissolved F concentrations from 48.8 to 3.5 mg I −1, and increased dissolved Mo concentrations from 1.9 to 3.9 mg I −1 in oil shale solid waste equilibrium waters. Chemical speciation of total soluble F and Mo concentrations in oil shale solid waste equilibrium waters indicated that F was present mainly as F −, NaF°, and CaF +. Molybdenum was present as MoO 4 2− and HMoO 4 −. Further results of this study suggested that dissolved F and Mo concentrations in oil shale solid waste equilibrium waters appear to be controlled by CaF 2 (fluorite) and CaMoO 4 (powellite), respectively.

Risk analysis of hazardous materials in oil shale

A future oil shale industry will be a massive solids-handling industry generating large amounts of hazardous materials. A risk analysis was performed on a hypothetical oil shale industry to aid in the formulation and management of research. The analysis considered occupational, public, and ecosystem risks for a steady-state one million barrels per day (160 cubic dekameters per day) industry. The risks for designated groups of the occupational workforce were statistically described by accident and injury rates for fatalities, accidents with days lost from work, and accidents with no days lost from work. Workforce diseases analyzed were cancers, silicosis, pneumoconiosis, chronic bronchitis, chronic airway obstruction, and high-frequency hearing loss. The miners represented the group with the largest fatality and the most serious accident rate. Lung disease from inhalation exposure to dust about the nuisance dust threshold limit value presented the most significant risk for future concerns. Public health inhalation risks were estimated for life-time cancer risks from As, Cd, Cr, Ni, polycyclic aromatic hydrocarbons, and radiation to be less than 10 −7 occurrences per person per year. An air pollution surrogate, sulfate, as a measure of all air pollution exposure, yielded a result of 10 −5 deaths per person per year with large uncertainties. Public health risks associated with oil shale solid waste were considered for leachates. Ecosystem risks considered impact on designator species, plant damage from sulfates, and disturbance in plant communities. The simple analysis approach indicated that the potential impact on the semi-arid, high-altitude ecosystem was minimal from air pollutants and land disturbances, but of potential concern for aquatic systems under extreme conditions. The methodology and treatment of uncertainties are oriented towards establishing research implications.