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Abstracts and Papers
The following abstracts summarize some of the papers, chapters, reports, etc. that are currently available from Envirometics, Inc. Abstracts are included on Odor Monitoring and Control, Combustion, Indoor Air Quality and Building Design Support, Dispersion Modeling, and Environmental Management. We have converted some of them so you can download them directly as PDF files. The others you can obtain by sending us an email. There may be a charge for some of the longer reports. A copy of the Adobe® Reader you need to view the PDF files is available by clicking on the icon in the panel on the left.
Indoor Air Quality and Building Design Support
Computational Computational Fluid Dynamics Analysis of Microscale Meteorological Flows for Air Quality Applications, J.D. McAlpine and M. Ruby.
Chapter 5C, Air Quality Modeling - Theories, Methodologies, Computational Techniques, and Available Databases and Software, Vol III, P. Zannetti (Ed.) (forthcoming: Fremont, CA: The Air and Waste Management Association and The EnviroComp Institute, 2006)
There is an ever-increasing need to simulate airflow at the micro-meteorological scale for environmental applications. Dispersion of pollutants around buildings and pedestrian level wind-speeds are two applications that concern environmental planners. Wind tunnels are still the main tool used, but computational methods are becoming more popular as a way to address these issues. Computational Fluid Dynamics (CFD) simulations are being used more often to model the surface layer of the atmosphere for environmental application. The use of CFD in this field is still experimental in nature and inherent weaknesses are apparent, but advances in computing and simulation methods are continually driving it towards becoming a reliable tool for predicting local air quality and other environmental conditions.
This review addresses today's common method of simulating the atmospheric surface layer in an urban environment using CFD. The features of the surface layer that are important for flow modeling are discussed as well as different methods for applying them in CFD. Different turbulence models and techniques for simulating the surface layer in CFD are reviewed as well. Current guidelines and processes for conducting a project are also described and discussed.
A copy of this paper will be available for downloading after formal publication. Advance copies may be made available to CFD practitioners on request.
Using CFD to Study Air Quality in Urban Microenvironments, J.D. McAlpine and M. Ruby. Chapter 1, Environmental Sciences and Environmental Computing, Vol II, P. Zannetti (Ed.) (Fremont, CA: The EnviroComp Institute, 2004)
The study of building effects on air quality has grown beyond stack plume downwash. The relative placement of air intakes and exhausts and cooling tower exhausts on buildings can significantly affect the indoor air quality. Earlier studies of effects on building air intakes have been limited to relatively simple situations, unable to treat the complex envelope of most buildings and building groups. Computational Fluid Dynamics (CFD) is becoming available as a tool to assist with modeling the airflow and dispersion of pollutants among complex urban geometries on the scale of a section of a building exterior up to several city blocks. This tool allows more accurate predictions of impacts over a range of meteorological scenarios and alternative building designs and placements relative to roadways and other pollutant sources. Recent projects are discussed to illustrate the capabilities of CFD in modeling urban microenvironments. The steps in a CFD application are presented including geometry and mesh creation, simulation of meteorological conditions, handling of pollutant sources, and post-processing visualization. The benefits and shortcomings of this approach are also discussed.
Download a copy of this paper (about 2.3 M).
Locating Air Intakes and Exhausts, Envirometrics Staff Paper (2004)
New ASHRAE standards require an investigation of local ambient air quality and documentation of design assumptions and calculations on measures taken to control the quality of the air supply. They also provide guidance on the minimum separation distances between air intakes and sources of air contaminants. The standard references AIHA and NFPA standards that apply specifically to laboratory hood exhausts. This report suggests the minimum distances provided may not always tbe adequate and gives minimum dilutions of exhaust sources that will provide adequate protection of the air supply for several frequently encountered sources.
Download a copy of this paper (about 80 k).
Computational Fluid Dynamics or Wind Tunnel Modeling?, J.D. McAlpine, Envirometrics, Inc.(2004)
CFD holds great promise for replacing the wind tunnel in coming years as the science behind CFD improves and computers become more powerful. Currently, CFD can provide results almost as accurate as a wind tunnel that are often more useful due to the sophisticated visualization and domain wide measurements characteristic of CFD. For building services, CFD is an effective tool for simulating wind climate to analyze pedestrian comfort, and pollution dispersion. It can also be used to assist engineers with natural ventilation design and building wind loading.
Download a copy of this paper (about 180 k).
Meeting the IBC Wind Loading Study Requirements, Envirometrics Staff Paper (2004)
The International Building Code recommends methods to be used to determine the wind-induced pressures on the face of a building. Estimates of wind pressures are calculated using equations provided in the code and compared to the results of computational fluid mechanics (CFD) modeling. Figures are included which illustrate the distribution of pressure across the faces of a model building. The values calculated by CFD are similar to, but provide more detail than those calculated by the more limited application equations.
Download a copy of this paper (about 100 k).
Download a copy of the graphics accompanying this paper (about 700 k).
Criteria for Determining the Impact of Wind Climatology on Pedestrian Comfort in an Urban Setting, J.D. McAlpine, Envirometrics, Inc.(2004)
Tall structures and the arrangements of tall structures have significant influence on the magnitude of wind velocities at the surface. Strong winds aloft can be brought down to the surface by their interaction with tall buildings. Channeling between large buildings can accelerate winds to high speeds. To the average person this may be only a nuisance, but to the frail or disabled this may be a real threat to health and safety. Therefore, environmental assessments of an existing or planned building or block of buildings should take into account the possibility of building influence on winds at the surface. Wind tunnel modeling using scale models has been the primary tool used to address these impacts for some time. Though proven to be accurate and reliable, this approach is not always feasible. Also, since measurements can only be taken at discrete points in the model, the more accuracy needed, the more expensive the modeling becomes. The advancements in computing power today have allowed for an alternative computational approach of wind tunnel modeling known as computational fluid dynamics (CFD). Though not as well-established as wind tunnel modeling, CFD offers a viable alternative that has advantages. CFD allows the investigator to analyze the full domain of modeling and present results in easy-to-understand graphics rather than several dozen discrete points, as with physical wind tunnel modeling. CFD modeling has been used by Envirometrics to assess comfort levels with respect to wind climate. This paper explores guidance criteria for evaluating pedestrian comfort in an urban setting.
Download a copy of this paper (about 60 k).
Alternatives to Chlorine for Cleaning Cooling Towers, Envirometrics Staff Paper (2004)
The new amendments to ASHRAE Standard 62-2001, Ventilation for Acceptable Indoor Air Quality, require a minium separation distance between cooling towers and outdoor air intakes or doors and windows that are a part of a natural ventilation design. However this minimum distance does not necessarily provide protection to building occupants from exposure to cooling tower contaminants. These contaminants may be either bacteria from an infection in the cooling tower sump or cleaning chemicals, generally chlorine, intended to protect against an infection. It has been our experience that attempting to provide such protection by adequate dilution of the cooling tower exhaust before entering an air intake is difficult, if not impossible. A better approach appears to be the use of alternatives to chlorine for maintaining cooling tower health.
Download a copy of this paper (about 150 k).
Ambient Air Filtration Options, Envirometrics Staff Paper (2004)
New ASHRAE standards require the use of particulate filters where air quality standards for particulate matter are exceeded and documentation of design decisions where other air quality standards are exceeded. This report reviews two filter arrangements currently used in healthcare, biotechnology and better commercial buildings and estimates annual costs for each. It reviews additional systems with higher control efficiency that might be applica-ble for new health care and biotechnology buildings and estimates annual costs.
Download a copy of this paper (about 100 k).
Standard Practice for Collection of Floor Dust for Chemical Analysis, D-5438-94, J.Hirsch, M. Ruby, J. Roberts, W.T. Budd. Annual Book of ASTM Standards (Philadelphia: American Society for Testing and Materials, 1994)
This practice covers a procedure for the collection of a sample of dust from carpets and bare floors that can be analyzed for lead, pesticides, or other chemical compounds and elements.
Click here to download a copy of this standard from the ASTM website.
Evaluation of HVS3 Sampler for Sampling Polycyclic Aromatic Hydrocarbons and Polychlorinated Biphenyls, J.C. Chung, S.M. Gordon, J.W. Roberts, W. Han, and M.G. Ruby. U.S. Environmental Protection Agency (EPA/600/SR-94/188), 1994
A polyurethane foam (PUF) filter was positioned after the cyclone in the High Volume Small Surface Sampler (HVS3) to determine the penetration of the cyclone by polycyclic aromatic hydrocarbons (PAH) and polychlorinated biphenyl (PCB) adsorbed on house dust. Less than 3% of the PAH and less than 5% of the PCB were found on the PUF filter compared to the cyclone catch. Therefore, the HVS3 without a PUF filter can quantitatively collect PAH and PCB in house dust. It was used to collect house dust samples from seven houses.
Human Exposure to Pollutants in the Floor Dust of Homes and Offices, J. Roberts, W. Budd, M. Ruby, D. Camann, R. Fortmann, R. Lewis, L. Wallace, and T. Spittler. J. Exposure Analysis and Environmental Epidemiology, Suppl. 1, 1992, pp. 127-146
This paper summarizes the literature on occurrence and exposure studies, sampling methods, control methods, and costs for pollutants in house dust. Lead, cadmium, arsenic, pesticides, and polycyclic aromatic hydrocarbons bind to particles and accumulate on surfaces, soil, and house dust. Dust samples have demonstrated mutagenic activity in in vitro test systems. Specific biologic and chemical components of the mixtures present in dust have been associated with allergic and sick building symptoms. Further, the exposure of toddlers to lead via the dust pathway may be greater than other major pathways. Thus sampling and analysis of house dust is important for characterizing exposure and evaluating potential risks.
Exposure from pollutants in air, soil, and dust are related but distinct. The concentration of pesticides in rug dust correlates with indoor air concentrations. However, in one study 13 pesticides were found in house dust that could not be detected in the indoor air. Pesticides that had not been commercially available for some years were found in the rug dust in field studies. Exposures from wood stoves, smoking, consumer products, traffic, industry, and Superfund sites may be more completely estimated if the exposures associated with the residues in house dust are assessed. Further, it is easier to sample an more effective to monitor exposure to many toxics in house dust than in indoor or outdoor air. Validated methods for sampling toxics in floor dust have been field tested.
E-mail Envirometrics, Inc. to request a copy of this paper.
A popular version of the information in this article is on the Scientific American website.
Odor Monitoring and Control
Estimating Odor Imapct With Computational Fluid Dynamics, M. Ruby and J.D. McAlpine. WEF Odors and Air Emissions 2004 (Alexandria, VA: Water Environment Federation, 2004), Session 3
The detection and nuisance concentrations of odors are frequently quoted in terms of dilutions from the initial source concentration. Meteorological dispersion modeling has been used to estimate the dilutions achieved between a release point, such as a stack, and a downwind receptor. Conventional models have proven to yield reasonable results for neutral and stable atmospheric conditions, within the acknowledged limitations of Gaussian dispersion models. However in regions with numerous buildings or sharp topography-induced turbulence, the Gaussian models are not able to provide results which take the turbulence into account. Computational Fluid Dynamics (CFD) is becoming available as a tool to assist with modeling the airflow and dispersion of pollutants among complex urban geometries on the scales of a section of a building exterior up to a few city blocks. This tool allows more accurate predictions of impacts within the regions of local turbulence. This can be especially important in urban areas where several buildings are within a mutual zone of influence and where air intakes are located on the top of a building with its own recirculation zone.
This paper illustrates the capabilities of CFD in modeling odor dispersion in urban microenvironments and compares the results of CFD modeling in actual source-neighbor building situations with results obtained using the conventional U.S. EPA model ISCST3 and the newer U.S. EPA model AERMOD in complex terrain modes.
A scaling factor has been frequently used to estimate the higher, short-term response to odors when using the 20 to 30-minute average dispersion coefficients of the conventional U.S. EPA models. CFD models report a steady state solution and the results also need to be adjusted to reflect the short-term odor response. This paper summarizes a peak-to-mean adjustment that is appropriate to CFD models that has been developed using an extensive data base collected by the U.S. EPA during its analysis of the proposal for one-hour ambient sulfur dioxide standards.
Download a copy of this paper (about 1 M).
Removal of Odorant Compounds by Packed Tower Scrubbing, M. Ruby, V. Stamper, and Y. Wang. Recent Developments and Current Practices in Odor Regulations, Controls, and Technology(Pittsburgh: Air And Waste Management Assoc., 1991), pp. 124-134
A pilot-scale wet scrubber has been constructed to make comparative tests of a new monolithic packing and a conventional random dumped packing. Both odor removal efficiency and pressure drop were measured at various gas and liquid flow rates. Hydrogen sulfide was removed from an air stream with a basic scrubbing liquor of sodium hydroxide and waster at at pH of 12.5. While the pressure drop through the monolithic packing was about one-tenth of that through an equal height bed of random dumped packing, the mass transfer coefficient was higher for the random dumped packing. Combining these two measurements, the pressure drop per transfer unit was found to be significantly lower for the monolithic packing. Thus the monolithic packing will be more cost efficient over the life of the packing.
Download a copy of this paper (about 500 kb).
Measurement of Odor Emissions from a Sewage Treatment Plant, M. Ruby, W. Prokop, and D. Kalman. Presented to the Annual Meeting of the Air Pollution Control Association, 1987
Odorous emissions from several locations in a sewage treatment plant were measured using the dynamic forced-choice olfactometer technique and specific components in the gases were identified using GC/MS. Measured odor sensory levels (ED50) were approximately 30 at the activated sludge aeration basins, 50 at the secondary clarifiers, 90 at the primary clarifiers and at the entrance to the aeration basins, and about 1000 at the discharge from the wet well. Hydrogen sulfide levels were approximately 0.5 ppm at each point except the wet well discharge, which was 6.5 ppm. The GC/MS analysis identified more than twenty major organic components of the emissions, but only ethyl mercaptan/dimethyl sulfide were found at concentrations above their odor threshold. Several other potentially odorous compounds with an odor threshold below the detection limit of the analytical technique were not identified.
Download a copy of this paper (about 500 kb).
Combustion
Estimates of NOx Emissions from Stationary Diesel Generators, W. Han and M. Ruby. presented to the Annual Meeting of the Pacific Northwest International Section of the Air Pollution Control Assn., 1992
Nitrogen oxides (NOx) emissions from stationary diesel engines are related to the maximum temperature during the combustion of the diesel fuel. Control measures for the reduction on NOx emissions include modifications to the engine operation and post-combustion chemical reactors. This paper provides data on the expected emissions from uncontrolled and modified diesel engines. Manufacturer’s emissions data and source-test data are compared. Alternative control technologies are discussed and cost estimates are provided.
E-mail Envirometrics, Inc. to request a copy of this paper.
Control of Particulate Matter Emissions from Diesel-Powered Vehicles, M. Ruby. presented to the Second World Bank Urban Air Quality Management Workshop, 1994
The more important sources of particulate matter emissions from diesel-powered vehicles are unburned fuel, lubricating oil, sulfur in the fuel, and dust resuspended from dust on the street. Engine-related emissions can be reduced by lowering the sulfur in the fuel, by improving the design of the engine so it can burn the fuel more completely and not burn the lubricating oils, by collecting the particulate matter emissions in a filter (or "trap"), and by burning the unburned fuel portion of the particulate matter in a catalytic oxidizer in the exhaust system. Engine manufacturers have achieved considerable success in developing advanced engine designs that reduce particulate mater emissions. Proper operation and timely maintenance are important in keeping the engines working as designed. Particulate traps that rely on external heating to regenerate have proven to require excessive maintenance but traps that rely on fuel additive catalysts for semi-continuous regeneration have been successful. Catalyst systems are able to satisfactorily reduce emissions from well-controlled engines when low sulfur fuel is used.
E-mail Envirometrics, Inc. to request a copy of this paper.
Dispersion Modeling
Determining the Proper Wind Sensor Height on a Building Using CFD, J.D. McAlpine and M. Ruby. Session 5.2, Technical Proceedings of the Annual Meeting of the Pacific Northwest International Section of the Air and Waste Management Assn.(Portland: Air and Waste Management Assn.:2004)
On-site meteorological data for air quality modeling must be collected at a power plant. Examination of the site led to the conclusion that no proper location existed on-site for the placement of a standard 10-meter meteorological tower due to local vegetation and buildings and other, nearby structures. Nor was there any off-site location available because the vicinity is built out. The only possible location of the tower is on top of the power plant itself. EPA meteorological guidance recommends that a fluid modeling effort be undertaken to demonstrate the suitability of a site when a tower is located on a building. Computational Fluid Dynamics (CFD) was used to determine the minimum height of the tower required to limit the influence of the building wake on the wind at the sensor.
Click here to download this paper (about 400 k).
Click here to download the graphics accompanying this paper (about 1.2 M).
Validation of COSMO, a COndensed Steam plume MOdel, M. Bassett, S. Hansen, and M. Ruby. Papers from the 9th World Clean Air Congress: Health and Ecological Effects, Vol. 5 (Pittsburgh: Air & Waste Management Assn., 1992), IU-16C.10
This paper describes the program structure and a test of the validity of COSMO, a model that estimates the visible outline of a condensing steam plume. This model is intended for the evaluation of wet, high temperature plumes, such as might be associated with a municipal waste incinerator or hogged-fuel boiler. The model was validated against field observations of 36 plumes collected by Argonne Labs. The performance was very good, with 34 correct predictions on plume height and 21 correct predictions on plume length. Many of the misses on plume length were from a site with less than adequate density of data.
E-mail Envirometrics, Inc. to request a copy of this paper.
Introduction to Atmospheric Dispersion Modeling, M. Ruby. from BASIC Dispersion Models, Software Tools for Air Pollution Studies (Seattle: Envirometrics, Inc., 1987)
This introductory chapter to a manual for several BASIC-language atmospheric dispersion models describes the principles behind three types of dispersion models: box, plume and puff. It describes the input data required for dispersion modeling, including wind speed, wind direction, stability class, and mixing height. Other important topics are discussed, including plume rise, wind shear, and modeling screening procedures.
Click here to download this chapter.
Environmental Management
Municipal Regulation of Medical Waste Incineration, W. Han, M. Ruby, D. Taflin, T. Chang, E. Cunningham. City of Seattle, Washington, 1993 - appx. 150 pp.
This report provides an in depth review of medical waste disposal practices, the possible effects on public health of medical waste incineration, and recommendations of actions that could be taken by a municipality in regulating medical waste disposal. It covers the characteristics of the medical waste stream, the various technologies for treatment of medical waste before disposal, federal, state, and local regulations on the handling and incineration of medical waste, measurements of emissions from both the local hospital incinerators and others reported in the scientific literature, an assessment of the health risks of incineration, a review of Seattle land use policies and requirements that effect medical waste disposal, three case studies of the regulation of medical waste incineration, and an analysis of six different regulatory approaches appropriate to a municipality, including amendments to the land use and solid waste handling codes. The report concluded that dioxins are the pollutant potentially of the greatest concern but that current control technology is capable of reducing the emissions of dioxins to acceptable levels.
Click here to download the Executive Summary of this report (about 18k).
E-mail Envirometrics, Inc. to to order a copy of the complete report. (Cost: $15 + sales tax)
Geostatistical Investigation of Arsenic-Contaminated Surface Soil Near the Tacoma Smelter, M. Ruby, M. Shaw, J. Maloney, P. Yuen. Proceedings of the Annual Meeting of the Pacific Northwest International Section of the Air and Waste Management Assn.(Seattle: Air and Waste Management Assn.:1995)
For many years, a copper smelter located in Tacoma, Washington utilized high arsenical ores. Arsenic in the stack gases and also escaping as a fugitive from handling and process sources resulted in arsenic-contaminated soil in the surrounding community. This study estimated the distribution of the levels of contamination from three soil sample sets, two collected for the EPA's Superfund remediation and one collected for this study. Maps were created of the soil arsenic concentrations using kriging techniques. The data are reported as probabilities the soil concentration will exceed selected levels. Maps are presented both for the concentration and for the probability that the concentration will exceed the urban background.
E-mail Envirometrics, Inc. to request a copy of this paper.
Click here to download a map of the estimated surface soil concentrations of arsenic (about 253k). See the paper for details on the way this map was generated and limitations to be aware of when interpreting the results.
Science vs. Technology: Determining Standards, M. Ruby - Science Behind Environmental Law Seminar, Chapter Ten (Seattle: Washington State Bar Assn., 1994)
The air quality standards established under the U.S. Clean Air Act are based on both protection of the public health and technological availability. This paper reviews the history of the development of air quality standards, and the meaning of key definitional elements of the standards. Examples are given of the bases for ambient air quality standards and technological standards for source emissions, including the newer "mixed" standards. The manner of implementing standards is described and alternatives to the current standards-based approach to air quality management is discussed.
Click here to download a copy of this chapter (about 41k).
Estimating the Value of Resources at Risk from Acid Deposition, M. Ruby. presented to the Annual Meeting of the Air Pollution Control Assn., 1986
This paper provides an estimate of both the magnitude of the resources at risk from acid deposition in Washington and, using a macro-environmental model and the best available information and expert opinion, the magnitude and probability of damage with the implementation of three control options. The ADEPT decision analysis model was used to make the comparison between the estimated costs of pollutant control programs for SO2 and NOx from the Centralia power plant and for NOx from motor vehicles and the reduced pollution damage to the natural resources of lakes, salmon spawning populations, commercial forests, and wilderness aesthetic values. The expected economic damages to resources included in the model are estimated to be $114.2 million, expressed as a net present value over the 30 years modeled. Expressed in terms of net social benefit, the total cost of controls is estimated to be $2.9 billion over the same period.
E-mail Envirometrics, Inc. to request a copy of this paper.
E-mail Envirometrics, Inc. to order a copy of the complete report. (Cost: $30 + sales tax)
Click here to download a map of the sensitivity of Washington soils to acid deposition (about 269k).
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