Spotting of Automotive Finishes from the Interactions Between Dry Deposition of Crustal Material and Wet Deposition of Sulfate

During the summer of 1988, General Motors Research Laboratories operated a mobile atmospheric research laboratory in Jacksonville, Florida to determine the cause of environmentally- related damage that occurs on automotive finishes In many parts of the U.S. The damage occurs as circular, elliptical, or irregular spots that appear as deposits or precipitates. The results of the present study show that a wetting event (rain or dew) is a prerequisite for damage to occur. Sulfuric acid contained in the rain or dew reacts on surfaces with drydeposited calcium which Is a common constituent of soli. As the droplets evaporate, a calcium sulfate precipitate forms on horizontal surfaces around the perimeter of the droplet. Subsequent washing of the surface may remove the precipitate, but on clearcoats, where the calcium sulfate was present, scars remain.     

Issues and Trends in Electrostatic Precipitation Technology for U.S. Utilities

The pace and direction of electrostatic precipitator (ESP) technology evolution in the United States will be governed by two key forces. The first is new clean air legislation passed by the U.S. Congress and signed by President Bush on November 15,1990. This law requires electric utilities to further reduce SO₂ and NO_x emissions, which may impact particulate controls. In addition, very fine (< 10 micron) participates and potentially toxic trace emissions from utility power plants may be regulated. The second major factor is the expected upsurge in new plant construction beginning in the late 1990s. Together, these forces should define the performance requirements and market for new ESPs.

This paper identifies and briefly describes technologies that the Electric Power Research Institute (EPRI) is developing to help U.S. utilities meet these challenges cost-effectively. Among the technologies addressed are: advanced digital voltage controls, flue gas conditioning, intermittent energization, temperature-controlledprecharging (i.e., two-stage ESP), wide plate spacing, positive energization of corona electrodes for hot-side ESPs, and integration of conventional ESPs with pulse-jet baghouses.     

Simultaneous Control of PCDD/PCDF,HCI and NOX Emissions from Municipal Solid Waste Incinerators with Ammonia Injection

This article Introduces a technology for the simultaneous control of the emissions of PCDD/ PCDF, hydrochloric acid (HCI) and nitrogen oxides (NO_x) from municipal solid waste (MSW) Incinerators. The technology uses ammonia as the control medium for all three pollutants. In this paper, the theoretical basis of the technology Is discussed. In addition, a bench-scale experiment proving the theory Is described and the practical application of the theory Is presented. Finally, further steps which are being taken to develop the technology for commercial application are detailed.     

Techniques for High-Quality Ambient Coarse Particle Mass Measurements

ABSTRACT

Several recent studies have shown associations between ambient concentrations of particle mass (PM) and rates of morbidity and mortality in the general population. These studies have raised the issue of quality of coarse mass (CM, PM between 2.5 and 10 µm) data used for these purposes. CM data may have precision three or more times worse than the associated PM _2.5 or PM₁₀ data, depending on the measurement method, PM _2.5 to PM ₁₀ ratios, and CM concentrations. CM is measured either as the difference between collocated _PM10 and _PM2.5 samplers or more directly with a dichotomous (virtual impactor) sampler. CM precision for the difference method is degraded due to the increased errors inherent with using the difference between two independent measurements, as well as the high PM_2.5 to PM₁₀ ratios (and low CM concentrations) typical of the eastern United States. The dichotomous sampler (dichot) makes a more direct measurement of CM, but there is a potential for significant postexposure loss of particles from unoiled CM dichot filters, as well as uncertainties in the dichot’s CM channel enrichment factor. Compared to the dichot, low-volume inertial impactor samplers such as the Harvard Impactor (HI) or PM2.5 Federal Reference Method (FRM) are simpler to operate and maintain, provide sharper cut points, and do not require oiled filters to prevent loss of CM from the filter during transport. With the recent interest in CM spatial and temporal variability with respect to PM health effects, we have developed modifications to the HI PM method to provide measurements of 24-hour PM with estimated CM precision of better than 5% CV and r² higher than 0.95, primarily by lowering field blank variability and increasing gravimetric analytical precision. These high-precision PM techniques are not limited to the HI sampler; they can also be applied to the _PM2.5 FRM sampler. The measurement methods described here can be applied to future PM studies to avoid the potential problems with exposure assessment caused by CM measurements that have poor precision.     

Removal of Chromium from Abrasive Blast Media by Leaching and Electrochemical Precipitation

ABSTRACT

Water is effective in leaching out Cr⁶⁺ from a mixture of paint powders and abrasive blast media. However, acids such as HNO₃, HCl, and H₂SO₄ significantly enhance the leaching procedure. Cr ions in the leaching solutions are successfully removed by electrochemical precipitation. The consumable Fe electrodes generate ferrous ions to cause the reduction of Cr⁶+ to Cr³+. Cr³+ ions along with Fe²+ and Fe³+ are then removed mainly by precipitation as Cr(OH)₃, Fe(OH)₂, and Fe(OH)₃ near the cathode where OH^- ions are generated by water electrolysis. The electrochemical process is capable of discharging low levels of Cr⁶+, less than 1 mg/L, without pH adjustment.     

Development and Demonstration of an Explicit Lumped-Parameter Biofilter Model and Design Equation Incorporating Monod Kinetics

Abstract

Biofiltration is an economical air pollution control (APC) technology, particularly suitable for the treatment of air-streams having high flow rates and low concentrations of volatile organic compounds (VOCs). This technology utilizes enzymatic catalysis at ambient conditions to mineralize such pollutants to CO₂, H₂O, and salts. A pilot-scale study conducted for more than 4 years investigated the development of a new biofiltration technology employing trickle bed air biofilters (TBABs). Following the completion of this experimental study, additional data analysis was performed to develop a simple lumped-parameter biofilter model, assuming first-order kinetics. This model related the observed biofilter performance to the principle independent physical, thermodynamic, and biochemical parameters. The initial model has subsequently been expanded to incorporate Monod kinetics. In this paper, the development and use of the final explicit lumped-parameter biofilter model and design equation, incorporating Monod kinetics, are presented. To facilitate the application of this model, practical procedures are also presented for the determination of VOC solubility, VOC biokinetic Monod parameters, and the maximum practical biofilter inlet VOC concentration.     

Treatment of benzene and n-hexane mixtures in trickle-bed air biofilters

Trickle-bed air biofilters (TBABs) are suitable for treatment of hydrophilic volatile organic compounds, but they pose a challenge for hydrophobic compounds. Three laboratory-scale TBABs were used for the treatment of an airstream contaminated with different ratios of n-hexane and benzene mixtures. The ratios studied were 1:1, 2:1, and 1:3 n-hexane:benzene by volume. Each TBAB was operated at a pH of 4 and a temperature of 20 degrees C. The use of acidic-buffered nutrient solution was targeted for changing the microorganism consortium to fungi as the main biodegradation element. The experimental plan was designed to investigate the long-term performance of the TBABs with an emphasis on different mixture loading rates, removal efficiency with TBAB depth, volatile suspended solids, and carbon mass balance closure. n-Hexane loading rate was kept constant in the TBABs for comparison reasons and ranged from 4 to 22 g/(m3 x hr). Corresponding benzene loadings ranged from 4 to 43 g/(m3 x hr). Generally, benzene behavior in the TBAB was superior to that of n-hexane because of its higher solubility. n-Hexane showed improved performance in the 2:1 mixing ratio as compared with the other two ratios.     

A rapidly equilibrating, thin film, passive water sampler for organic contaminants; characterization and field testing

Improving methods for assessing the spatial and temporal resolution of organic compound concentrations in marine environments is important to the sustainable management of our coastal systems. Here we evaluate the use of ethylene vinyl acetate (EVA) as a candidate polymer for thin-film passive sampling in waters of marine environments. Log K_EVA−W partition coefficients correlate well (r² = 0.87) with Log K_OW values for selected pesticides and polychlorinated biphenyls (PCBs) where Log K_EVA−W = 1.04 Log K_OW + 0.22. EVA is a suitable polymer for passive sampling due to both its high affinity for organic compounds and its ease of coating at sub-micron film thicknesses on various substrates. Twelve-day field deployments were effective in detecting target compounds with good precision making EVA a potential multi-media fugacity meter.