1 639 kr
Skickas inom 11-20 vardagar
Dennis A. Clifford – författare
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3 produkter
3 produkter
1 639 kr
Skickas inom 11-20 vardagar
Since 1997, several perchlorate treatment technologies have proven to be technically feasible at drinking-water treatment scale: biological reduction, ion exchange, reverse osmosis (RO) membranes, and granular activated carbon (GAC). The objectives of this project were to demonstrate the long-term performance of conventional ion-exchange technology for perchlorate removal and evaluate three disparate alternatives (chemical, biological, electrolytic) for brine treatment and reuse. This project evaluated three fundamentally different brine treatment and reuse processes. The first process, the biological brine treatment system, operated as a sequencing batch reactor (SBR). The second process, the physical/chemical brine treatment system, employed a high-pressure and high-temperature catalytic process to reduce the nitrate and perchlorate in the spent brine. The last process, a simple bipolar electrochemical cell, electrolytically reduced the perchlorate and/or nitrate present in the spent ion exchange brine. Potential users of the treatment technologies developed in this research include all municipalities required to treat perchlorate- and/or nitrate-contaminated groundwater. The treatment processes evaluated in this research are applicable to both existing and future ion exchange systems, and could be applied to decontaminating high-pressure membrane reject streams as well.- Häftad, 2007
501 kr
Skickas inom 11-20 vardagar
In order to establish effective treatment removal strategies for arsenic, it is important to know the actual concentrations of As(III) and As(V) in drinking waters. Due to its anionic character, As(V) can be removed more easily than As(III). The distribution of As(III) and As(V) species depends greatly on the abundance of redox-active solids, especially organic carbon, the activity of microorganisms, and the extent of diffusion of O2 from the atmosphere. In strongly reducing aquifers, As(III) is the dominant species based on the thermodynamic considerations, whereas As(V) is the more stable oxidation state under oxic conditions or in oxygenated waters.? Based on extensive experimental results in Fe(II)-contaminated challenge water, it was found that EDTA-HAc could be used to preserve the arsenic species for at least 28 days in opaque plastic bottles. Although the alternative preservatives, H2SO4 and H3PO4, successfully preserved the original As(III)/(V) speciation under some conditions, these preservatives were generally unsuccessful for the desired 28-day period under reducing and oxidizing conditions in the sample pH range of 6.5?V8.4 and in the presence of 3 mg/L Fe(II). A comprehensive, systematic study was conducted to determine the effect of ferrous iron on the stability of arsenic species. Among the promising preservatives described in the literature, H2SO4, H3PO4, EDTA, and EDTA-HAc were chosen for this study.? The combined results of two AwwaRF arsenic analysis projects 'Field Speciation Method for Arsenic Inorganic Species' and this project, Preservation of Arsenic Species have yielded a method for immediate field-speciation and a preservation technique for speciation within 30 days of sampling. Limited field verifications of these methods, which give statistically indistinguishable results, have been completed.
