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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 Processes (AOPs) and their Potential Against Micropollutants: Fundamentals and Practical Aspects in Wastewater Treatment
Endocrine disrupting chemicals (EDCs) as well as pharmaceuticals and personal care products (PPCPs) constitute sub-categories of a larger group of targeted compounds in water treatment known as micropollutants. Micropollutants are mostly organics and, depending upon their structure and by that their refractory potency, often escape treatment across conventional water or wastewater plants including those utilizing biological processes. This is attributed to the toxicity of such compounds to the active microorganisms of a biological process. While they may assimilate compounds that make up the biodegradable fraction of the wastewater, they usually fail to metabolize micropollutants of complex structure. One of the most effective alternatives to treat these micropollutants is the use of destructive technologies known as Advanced Oxidation Technologies (AOTs) or Processes (AOPs).
AOPs can treat any organic compound in relatively clean waters. Studies also show that, at the appropriate dosages, AOPs can also decontaminate heavily polluted and challenging waste streams. There are numerous applications of the Fenton reagent, for example, successfully treating industrial wastewaters high in COD or in color content. Similar to conventional or direct oxidation processes AOPs are based on oxidation-reduction (redox) reactions. What distinguishes AOPs from direct redox systems, however, is the generation of highly reactive, short-lived, transient species known as radicals (i.e., the hydroxyl radical, •OH). These attack and readily destroy, almost all organics present in water. AOPs are potent because the thermodynamics and kinetics of the reactions between radicals and organics are very favorable and fast. To form these radicals via an AOP one needs a primary chemical (oxidant) and an activator that will excite that primary chemical. In most AOPs, the limiting step is the first reaction between the oxidant and the activator upon which the initial radical species are formed (initiation reaction). This particular step and the species involved are usually what define a particular AOP and also differentiate one AOP from the other. For more information on AOPs, including discussion of the following topics, you may contact us at ganipsitakis@chastainskillman.com .
- Mechanisms and variations of AOPs based on different combinations of primary chemicals and activators.
- Common chemicals or peroxides: characteristics, advantages and disadvantages.
- Ultraviolet (UV) radiation: lamps and energy efficiency, engineered systems, energy demand for disinfection and for destruction of micropollutants.
- Overview of research studies targeting micropollutants such as phenols, atrazine, ammonium ion, arginine, creatinine, and E.coli.
- Cost and other implications resulting from the use of AOPs.
- Water quality characteristics and how they affect AOPs’ efficiency (i.e., inhibitors or radical sinks).
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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