Brian P. Dwyer

Removal of As, Mn, Mo, Se, U, V and Zn from groundwater by zero-valent iron in a passive treatment cell: reaction progress modeling

Three treatment cells were operated at a site near Durango, CO. One treatment cell operated for more than 3 years. The treatment cells were used for passive removal of contamination from groundwater at a uranium mill tailings repository site. Zero-valent iron [Fe(0)] that had been powdered, bound with aluminosilicate and molded into plates was used as a reactive material in one treatment cell. The others used granular Fe(0) and steel wool. The treatment cells significantly reduced concentrations of As, Mn, Mo, Se, U, V and Zn in groundwater that flowed through it. Zero-valent iron [Fe(0)], magnetite (Fe3O4), calcite (CaCO3), goethite (FeOOH) and mixtures of contaminant-bearing phases were identified in the solid fraction of one treatment cell. A reaction progress approach was used to model chemical evolution of water chemistry as it reacted with the Fe(0). Precipitation of calcite, ferrous hydroxide [Fe(OH)2] and ferrous sulfide (FeS) were used to simulate observed changes in major-ion aqueous chemistry. The amount of reaction progress differed for each treatment cell. Changes in contaminant concentrations were consistent with precipitation of reduced oxides (UO2, V2O3), sulfides (As2S3, ZnS), iron minerals (FeSe2, FeMoO4) and carbonate (MnCO3). Formation of a free gas phase and precipitation of minerals contributed to loss of hydraulic conductivity in one treatment cell.

Collection Drain and Permeable Reactive Barrier for Treating Uranium and Metals from Mill Tailings near Durango, Colorado

Publisher Summary This chapter presents a study in which contaminated water flowing from a uranium mill tailings repository near Durango, Colorado, was collected in a drain and piped to a system of permeable reactive barriers (PRBs). The PRBs were constructed in two configurations, leach fields and baffled tanks and ZVI was used in three forms, foam plates, granular, and steel wool. All three forms of ZVI produced chemically reducing conditions and removed most contaminants [arsenic (As), cadmium, copper (Cu), molybdenum (Mo), nitrate, radium-226, selenium (Se), uranium (U), vanadium (V), and zinc (Zn)], but equal volumes of foam plates or granular ZVI were more efficient than steel wool. A baffled tank containing ZVI removed contaminants more effectively than the leach field system and allowed easy replacement of the ZVI. The chemical analysis indicated that significant quantities of Ca, inorganic carbon, and sulfur were deposited in the PRB in addition to the contaminants. Calcite, iron (Fe)-calcite, goethite, magnetite, ferrihydrite, and a U-V-silicon-rich Fe-oxide phase (or mixture of phases) were identified using X-ray diffraction and electron microprobe methods. Magnesium, manganese (Mn), 226 Ra, and strontium were deposited in the PRB, possibly in solid solution with carbonate minerals. Some constituents, including aluminum, chromium, Cu, Fe, Mn, and sodium, were partially leached from the ZVI foam plates. Arsenic and Se concentrations in the ZVI foam plates were highest near the inlet, indicating rapid deposition in the PRB. Concentrations of other constituents, including Ca, Mo, U, V, and Zn, were also high near the inlet, but high concentrations extended some distance into the PRB, suggesting slightly longer residence times were required to remove them.

Laboratory and field scale demonstration of reactive barrier systems

In an effort to devise a cost efficient technology for remediation of uranium contaminated groundwater, the Department of Energy`s Uranium Mill Tailings Remedial Action (DOE-UMTRA) Program through Sandia National Laboratories (SNL) fabricated a pilot scale research project utilizing reactive subsurface barriers at an UMTRA site in Durango, Colorado. A reactive subsurface barrier is produced by placing a reactant material (in this experiment, metallic iron) in the flow path of the contaminated groundwater. The reactive media then removes and/or transforms the contaminant(s) to regulatory acceptable levels. Experimental design and results are discussed with regard to other potential applications of reactive barrier remediation strategies at other sites with contaminated groundwater problems.

From benchtop to raceway : spectroscopic signatures of dynamic biological processes in algal communities.

The search is on for new renewable energy and algal-derived biofuel is a critical piece in the multi-faceted renewable energy puzzle. It has 30x more oil than any terrestrial oilseed crop, ideal composition for biodiesel, no competition with food crops, can be grown in waste water, and is cleaner than petroleum based fuels. This project discusses these three goals: (1) Conduct fundamental research into the effects that dynamic biotic and abiotic stressors have on algal growth and lipid production - Genomics/Transcriptomics, Bioanalytical spectroscopy/Chemical imaging; (2) Discover spectral signatures for algal health at the benchtop and greenhouse scale - Remote sensing, Bioanalytical spectroscopy; and (3) Develop computational model for algal growth and productivity at the raceway scale - Computational modeling.

Treatment of Oil & Gas Produced Water.

Production of oil and gas reserves in the New Mexico Four Corners Region results in large volumes of “produced water”. The common method for handling the produced water from well production is re-injection in regulatory permitted salt water disposal wells. This is expensive (~

Structural Code Considerations for Solar Rooftop Installations

5/bbl.) and does not recycle water, an ever increasingly valuable commodity. Previously, Sandia National Laboratories and several NM small business tested pressure driven membrane-filtration techniques to remove the high TDS (total dissolved solids) from a Four Corners Coal Bed Methane produced water. Treatment effectiveness was less than optimal due to problems with pre-treatment. Inadequate pre-treatment allowed hydrocarbons, wax and biological growth to foul the membranes. Recently, an innovative pre-treatment scheme using ozone and hydrogen peroxide was pilot tested. Results showed complete removal of hydrocarbons and the majority of organic constituents from a gas well production water.

Method and apparatus for constructing an underground barrier wall structure

Residential rooftop solar panel installations are limited in part by the high cost of structural related code requirements for field installation. Permitting solar installations is difficult because there is a belief among residential permitting authorities that typical residential rooftops may be structurally inadequate to support the additional load associated with a photovoltaic (PV) solar installation. Typical engineering methods utilized to calculate stresses on a roof structure involve simplifying assumptions that render a complex non-linear structure to a basic determinate beam. This method of analysis neglects the composite action of the entire roof structure, yielding a conservative analysis based on a rafter or top chord of a truss. Consequently, the analysis can result in an overly conservative structural analysis. A literature review was conducted to gain a better understanding of the conservative nature of the regulations and codes governing residential construction and the associated structural system calculations.