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These in-depth documents explore the reasons and the methods behind the work we do. They are meant for use within the industry and may not lend themselves to easy-reading the way our articles do. Like our articles, these white papers are all copyrighted by Chastain-Skillman.
Application of CALINE4 to roadside NO/NO2 transformations
The CALINE4 roadway dispersion model has been applied to concentrations of NOx and NO2 measured near Gandy Boulevard in Tampa, FL (USA) during May 2002. A NOx emission factor of 0.86 gr mi−1 was estimated by treating NO+NO2 (NOx) as a conserved species and minimizing the differences between measured and calculated NOx concentrations. This emission factor was then used to calculate NO2 concentrations using the NO/NO2 transformation reactions built into CALINE4. A comparison of measured and calculated NO2 concentrations indicates that for ambient O3 concentrations less than 40 ppb the model under-predicts the chemical transformation of NO. The enhanced transformation of NO may be due to reactions of NO with oxidants such as peroxy radicals that are present either in the atmosphere or in vehicle exhaust.
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Advanced Oxidation
Chemical oxidation is a treatment process that has the potential to completely destroy harmful non-biodegradable organic contaminants in water. The so-called Advanced Oxidation Technologies (AOTs) are among the most effective chemical oxidation processes and play a crucial role in water treatment. In AOTs, the reactions follow a specific oxidation pathway, which, in most of the cases, is initiated by the formation of free hydroxyl radicals. The hydroxyl radicals are extremely reactive and readily attack and destroy harmful organic molecules. The final products are carbon dioxide, water and, depending upon the chemical composition of the precursor, other ionic inorganic residues such as chloride and nitrate. The latter species are considered environmentally acceptable, since their final concentration is low. The complete oxidation of the organic carbon of the targeted pollutants to the inorganic of carbon dioxide is called “mineralization” and is a feasible outcome at optimum conditions of most AOTs. Typical examples of Advanced Oxidation Technologies (AOTs) include activated ozone, UV/H2O2, sonolysis, the Fenton Reagent (Fe2+/H2O2), Fenton-like reactions (Fe3+/H2O2 with and without UV-light radiation), electron beams (γ-irradiation) and TiO2-photocatalysis. One should not confuse AOTs with conventional oxidation reactions such as low pH ozonation, chlorination and reaction with permanganate. The difference between the two lies upon the species responsible for the transformation of the target compounds and such differences translate into different kinetics and overall extent of transformation. In general, AOTs are much faster and more powerful than conventional reactions. On the other hand, AOTs are generally more costly and, when one is not limited by time and stringent contaminant levels, a conventional oxidizing reagent may be a more viable option. This presentation provides an overview of AOTs including the activation of chemicals such as ozone, hydrogen peroxide, sodium/potassium persulfate and potassium peroxymonosulfate. The latter two, when activated, release another extremely powerful radical in water; the sulfate radical. Activation techniques include mainly the use of transition metal catalysts or ultraviolet (UV) irradiation.
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Phase Anaerobic Digestion to Achieve Class A Biosolids
In anticipation of reaching full treatment plant operating capacity and changes in the biosolids disposal regulations, the City of Lakeland, Florida decided to pursue improvements and expansion of the existing solids processing at the Glendale WRF. A design memorandum was prepared for the City presenting various processing options. Several meetings held with City representatives, representatives from Chastain-Skillman, Inc., and some of the process vendors. The selected process (2PAD with Egg-Shaped Digester) was then designed into the existing facility and is under construction. The purpose of this paper is to present some of the options considered during the selection process, to show how these options were integrated into the final design, and also to show how a proprietary process can be included in competitively bid projects.
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Mold 101: An Overview
In the last two years, a wave of multimillion-dollar verdicts, new legislation and media attention have portrayed mold as the next toxic tort. Building owners, builders, suppliers, and occupants have become familiar with the hazards and exposures associated with mold. This paper provides a summary overview of the basic composition of mold and conditions conducive to mold growth, common claims and parties involved in mold litigation, practical strategies for addressing and reducing mold infestation, and available insurance coverage for mold claims.
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