Sandip Chattopadhyay

Modeling leaching of viruses by the Monte Carlo method

A predictive screening model was developed for fate and transport of viruses in the unsaturated zone by applying the final value theorem of Laplace transformation to previously developed governing equations. A database of input parameters allowed Monte Carlo analysis with the model. The resulting kernel densities of predicted attenuation during percolation indicated very small, but finite probabilities of failure for all homogeneous USDA classified soils to attenuate reovirus 3 by 99.99% in one-half meter of gravity drainage. The logarithm of saturated hydraulic conductivity and water to air-water interface mass transfer coefficient affected virus fate and transport about 3 times more than any other parameter, including the logarithm of inactivation rate of suspended viruses. Model results suggest extreme infiltration events may play a predominant role in leaching of viruses in soils, since such events could impact hydraulic conductivity. The air-water interface also appears to play a predominating role in virus transport and fate. Although predictive modeling may provide insight into actual attenuation of viruses, hydrogeologic sensitivity assessments for the unsaturated zone should include a sampling program.

Evaluation of Blast Furnace Slag as a Means of Reducing Metal Availability in a Contaminated Sediment for Beneficial Use Purposes

An attractive option for the management of dredged sediment involves the use of dredged sediment for beneficial use purposes, such as for fill material. Treatment (chemical amendment) of contaminated sediment may be necessary to limit the environmental and human availability (bioaccessibility, leachability, plant uptake) of heavy metals associated with the contaminated sediment before it is placed. A laboratory study was conducted to investigate the effect of admixing a specific chemical amendment (blast furnace slag) with slightly contaminated fresh-water sediment for reducing metal availability. Initial characterization tests of the un-amended sediment showed that the some of the metals analyzed were present in relatively available (non-residual) forms. Although sulfide was present in the un-amended sediment, the amount was not sufficient to bind all of the available metals. A series of metal availability testing methods indicated that the amendment of the sediment with blast furnace slag (4% on a dry weight ratio basis) had the potential to slightly reduce the availability of some, but not all of the available metals associated with the sediment. Results of the column and batch leaching tests showed that leachability of certain metals, such as barium, nickel and zinc, was reduced by the amendment, but the leachability of copper increased. The effect of the amendment for decreasing bioaccessibility for lead and arsenic was not demonstrated. The amended soil had a detrimental effect on most of the plant species that were evaluated. The metal availability results for the plant uptake tests were also mixed, with slightly lower uptake of certain metals by corn grown within the amended sediment.

Engineering and Economic Assessment of CO2 Sequestration in Saline Reservoirs

Publisher Summary Concern over the potential effects of greenhouse gases such as carbon dioxide (CO2) on global climate has triggered extensive studies on ways to reduce emissions of these gases. CO2 disposal in deep saline reservoirs has emerged as one of the most attractive long-term, technology-based options for mitigating greenhouse gas emissions. One way to reduce greenhouse gas emissions is to capture and sequester CO2 produced by combustion of fossil fuels from power plants and other large sources of CO2 emissions. An engineering and economic assessment was conducted to review the status of existing technologies that could be used to sequester CO2, develop a preliminary engineering concept for accomplishing the required operations, estimate capital and operating costs for sequestration systems under various design conditions, and outline regulatory and project implementation aspects. This review did not identify any technical obstacles to implementing CO2 sequestration. Future work will involve implementation of these concepts at a large power plant to characterize and develop the site for potential future CO2 injection and monitoring. This chapter describes the principal findings of the evaluation of the engineering requirements and economic variables for the deployment of CO2 capture and sequestration in on-shore saline reservoirs.

Evaluation of CO2 Sequestration in Saline Formations Based on Geochemical Experiments and Modeling

Publisher Summary This chapter presents results of a recently completed study in collaboration with the U.S. Department of Energys (DOE) National Energy Technology Laboratory (NETL) to conduct research on the feasibility of CO 2 sequestration in deep saline formations. The overall objective of this geochemical study was to enhance understanding of the interactions between injected CO 2 , formation fluids, and rock media based on laboratory experiments and geochemical simulations. Once injected into reservoirs, a large portion of the CO 2 may remain as a separate phase and float towards the top of the reservoir due to density contrasts, while some may dissolve in the formation fluid. It also investigated the potential for long-term sequestration of CO 2 in a deep, regional host rock formation and evaluated the compatibility of overlying caprock with injected CO 2 with regard to its effectiveness as a barrier against upward migration of the injectate. Experiments were conducted using rock samples from different potential host formations and overlying caprocks, as well as certain pure mineral specimens to evaluate specific mineral reactions. Reaction vessels containing a pure solid phase or mechanical mixture of phases, and liquid were pressurized with CO 2 or a mixture of either N 2 and CO 2 , or N 2 , CO 2 , and SO 2 . The duration of the experiments was one to three months at pressures consistent with deep reservoirs, and temperatures of either 50°C (typical) or 150°C (elevated). It was concluded from the experiments and geochemical modeling calculations that the potential for adverse effects of CO 2 injection into capped, sandstone formations is low.

Geologic Storage of CO 2 from Refining and Chemical Facilities in the Midwestern United States

Publisher Summary This chapter describes the process of geologic storage of CO2 from refineries and chemical plants in the midwestem United States. Three locations in the midwestem United States were evaluated for saline reservoir sequestration of CO2 transported from refineries and chemical plants along existing pipeline rights of way. Based on formation volume calculations, the potential storage capacity in a single formation, the Mt. Simon Sandstone, is in the range of several billion tons. Compositional reservoir simulations were completed to predict the formation pressures, CO2 spreading, and dissolution following injection. Injectivity at all sites was sufficient for more than 1 mt/year/well of CO2 without exceeding the fracture pressure limits, and no leakage of CO2 into shallower horizons was predicted. A horizontal injection well scenario showed a smaller increase in reservoir pressure than vertical wells. The geochemical evaluation included a summary of the brine chemistry and mineralogy of the reservoir and caprock formations. Equilibrium geochemical simulations for several scenarios did not indicate any adverse reactions as a result of CO2 injection. A preliminary economic and engineering assessment of several injection scenarios showed that the cost of CO2 dehydration, compression, transport, and injection is nearly

Advances in encapsulation technologies for the management of mercury-contaminated hazardous wastes ☆

20 per ton, excluding any capture costs. The largest capital cost is in compression and pipeline systems, and the largest operational cost is that of compression. System costs may be reduced by optimizing the location of storage reservoirs closer to the emission sources or through development of a regional shared transport network and storage site.