Improving Baghouse Performance at the Monticello Generating Station

At the Monticello station, operated by the Texas Utilities Generating Company, lignite coal obtained locally in Titus and Hopkins Counties fuels each of the three units. Units 1 and 2 are identical 575-MW Combustion Engineering (CE) boilers, each of which discharges its effluent to a 36- compartment shake/deflate cleaned baghouse paralleled with four electrostatic precipitators (ESP). Unit 3 is a larger boiler and is followed by an ESP and a scrubber. The Unit 1 and 2 baghouses were designed to clean 80 percent of the flue gas. Since startup, these baghouses have regularly experienced flange-to-flange pressure drops in excess of 10 in. H₂O, with large opacity spikes caused by ash bleeding through the bags after compartment cleanings. Because of higher-than-expected pressure drop, the baghouses receive only about 45-50 percent of the flue gas. Analysis has shown the Monticello lignite ash significantly differs from most other coal ashes. Testing has shown that the Monticello ash is not filtered effectively by many "standard" bag materials. However, this testing indicates that there are fabrics that show promise of eliminating the ash bleedthrough with little pressure drop penalty. Testing has also shown that injection of low concentrations (10-15 ppm) of ammonia (NH₃) into the flue gas significantly decreases ash bleedthrough, so that with NH₃ injection "standard" bag materials may perform adequately. Currently, fullcompartment testing of four fabrics, with and without NH₃ injection, is under way at the Unit 1 baghouse. The research conducted at the Monticello station is reviewed in this paper and the encouraging results from the full-compartment tests are presented.     

Comparative assessment of wet and dry garment cleaning Part 1. Environmental and human health assessment

Water-based cleaning of specialty garments is emerging as a potential alternative to dry cleaning. Perchloroethylene, the solvent used in dry cleaning, poses significant human and ecosystem health concerns. This paper is part 1 of a two part series that analyzes the key environmental, human health, performance, economic, and regulatory factors which influence the future of the garment cleaning industry. This paper inventories the environmental releases and wastes associated with the consumption of perchloroethylene in modern dry cleaning machines which ranges from 2.0 to 5.2 kg per 100 kg of clothing cleaned. In addition, water, electricity, and other inputs for both perchloroethylene-based and water-based garment cleaning are compared using data from previous demonstration projects. Toxicological and epidemiological studies provide evidence for the carcinogenicity of perchloroethylene although this classification is controversial. Cancer risks at low levels of exposure associated with modern dry cleaning equipment and good housekeeping practices are unknown and require further investigation. Regardless of these uncertainties, water-based cleaning is preferable to dry cleaning from a human and environmental health perspective.     

Achieving the promise of transdisciplinarity: a critical exploration of the relationship between transdisciplinary research and societal problem solving

Transdisciplinarity is often presented as a way to effectively use scientific research to contribute to societal problem solving for sustainability. The aim of this paper is to critically explore this statement. This is done in two ways. First, a literature survey of transdisciplinary research is used to identify the assumptions that underlie the positive relationship between transdisciplinarity and societal problem solving for sustainability. This mapping identifies the claim that in-depth participation of users and the integration of relevant knowledge from both practice and research in real-world problem contexts produce socially robust results that contribute to sustainability. Second, the ability to live up to this claim is presented and discussed in five case study projects from Mistra Urban Futures, a transdisciplinary center in Göteborg, Sweden. The conclusions show that transdisciplinary processes, which fulfill the above conditions, do produce different types of socially robust knowledge, but this does not necessarily result in the ability to influence change in a sustainable direction. This instead creates a paradox in that the participation of stakeholders and the integration of knowledge from diverse sources require spaces that are both embedded in and insulated from practice and science proper. Such spaces produce results that are not easily aligned with sector-based target groups and formal policy processes. Institutionalizing transdisciplinarity in a boundary organization therefore solves some problems regarding participation and balanced problem ownership. However, it also creates new, hybrid problems, regarding knowledge transfer and scalability, which bridge the boundaries and challenge the praxis of planning and policy making.     

Regulated and unregulated emissions from modern 2010 emissions-compliant heavy-duty on-highway diesel engines

The U.S. Environmental Protection Agency (EPA) established strict regulations for highway diesel engine exhaust emissions of particulate matter (PM) and nitrogen oxides (NO_x) to aid in meeting the National Ambient Air Quality Standards. The emission standards were phased in with stringent standards for 2007 model year (MY) heavy-duty engines (HDEs), and even more stringent NO_X standards for 2010 and later model years. The Health Effects Institute, in cooperation with the Coordinating Research Council, funded by government and the private sector, designed and conducted a research program, the Advanced Collaborative Emission Study (ACES), with multiple objectives, including detailed characterization of the emissions from both 2007- and 2010-compliant engines. The results from emission testing of 2007-compliant engines have already been reported in a previous publication. This paper reports the emissions testing results for three heavy-duty 2010-compliant engines intended for on-highway use. These engines were equipped with an exhaust diesel oxidation catalyst (DOC), high-efficiency catalyzed diesel particle filter (DPF), urea-based selective catalytic reduction catalyst (SCR), and ammonia slip catalyst (AMOX), and were fueled with ultra-low-sulfur diesel fuel (~6.5 ppm sulfur). Average regulated and unregulated emissions of more than 780 chemical species were characterized in engine exhaust under transient engine operation using the Federal Test Procedure cycle and a 16-hr duty cycle representing a wide dynamic range of real-world engine operation. The 2010 engines’ regulated emissions of PM, NO_X, nonmethane hydrocarbons, and carbon monoxide were all well below the EPA 2010 emission standards. Moreover, the unregulated emissions of polycyclic aromatic hydrocarbons (PAHs), nitroPAHs, hopanes and steranes, alcohols and organic acids, alkanes, carbonyls, dioxins and furans, inorganic ions, metals and elements, elemental carbon, and particle number were substantially (90 to >99%) lower than pre-2007-technology engine emissions, and also substantially (46 to >99%) lower than the 2007-technology engine emissions characterized in the previous study.

Implications:?Heavy-duty on-highway diesel engines equipped with DOC/DPF/SCR/AMOX and fueled with ultra-low-sulfur diesel fuel produced lower emissions than the stringent 2010 emission standards established by the U.S. Environmental Protection Agency. They also resulted in significant reductions in a wide range of unregulated toxic emission compounds relative to older technology engines. The increased use of newer technology (2010+) diesel engines in the on-highway sector and the adaptation of such technology by other sectors such as nonroad, displacing older, higher emissions engines, will have a positive impact on ambient levels of PM, NOx, and volatile organic compounds, in addition to many other toxic compounds.     

Regulated and unregulated emissions from highway heavy-duty diesel engines complying with U.S. Environmental Protection Agency 2007 emissions standards

As part of the Advanced Collaborative Emissions Study (ACES), regulated and unregulated exhaust emissions from four different 2007 model year U.S. Environmental Protection Agency (EPA)-compliant heavy-duty highway diesel engines were measured on an engine dynamometer. The engines were equipped with exhaust high-efficiency catalyzed diesel particle filters (C-DPFs) that are actively regenerated or cleaned using the engine control module. Regulated emissions of carbon monoxide, nonmethane hydrocarbons, and particulate matter (PM) were on average 97, 89, and 86% lower than the 2007 EPA standard, respectively, and oxides of nitrogen (NOx) were on average 9% lower. Unregulated exhaust emissions of nitrogen dioxide (NO2) emissions were on, average 1.3 and 2.8 times higher than the NO, emissions reported in previous work using 1998- and 2004-technology engines, respectively. However, compared with other work performed on 1994- to 2004-technology engines, average emission reductions in the range of 71-99% were observed for a very comprehensive list of unregulated engine exhaust pollutants and air toxic contaminants that included metals and other elements, elemental carbon (EC), inorganic ions, and gas- and particle-phase volatile and semi-volatile organic carbon (OC) compounds. The low PM mass emitted from the 2007 technology ACES engines was composed mainly of sulfate (53%) and OC (30%), with a small fraction of EC (13%) and metals and other elements (4%). The fraction of EC is expected to remain small, regardless of engine operation, because of the presence of the high-efficiency C-DPF in the exhaust. This is different from typical PM composition of pre-2007 engines with EC in the range of 10-90%, depending on engine operation. Most of the particles emitted from the 2007 engines were mainly volatile nuclei mode in the sub-30-nm size range. An increase in volatile nanoparticles was observed during C-DPF active regeneration, during which the observed particle number was similar to that observed in emissions of pre-2007 engines. However, on average, when combining engine operation with and without active regeneration events, particle number emissions with the 2007 engines were 90% lower than the particle number emitted from a 2004-technology engine tested in an earlier program.     

Field and laboratory investigations on the effects of road salt (NaCl) on stream macroinvertebrate communities

Field and laboratory experiments were conducted to examine the effects of road salt (NaCI) on stream macroinvertebrates. Field studies investigated leaf litter processing rates and functional feeding group composition at locations upstream and downstream from point source salt inputs in two Michigan, USA streams. Laboratory studies determined the effects of increasing NaCl concentrations on aquatic invertebrate drift, behavior, and survival. Field studies revealed that leaves were processed faster at upstream reference sites than at locations downstream from road salt point source inputs. However, it was sediment loading that resulted in partial or complete burial of leaf packs, that affected invertebrate activity and confounded normal leaf pack colonization. There were no significant differences that could be attributed to road salt between upstream and downstream locations in the diversity and composition of invertebrate functional feeding groups. Laboratory drift and acute exposure studies demonstrated that drift of Gammarus (Amphipoda) may be affected by NaCl at concentrations greater than 5000 mg/l for a 24-h period. This amphipod and two species of limnephilid caddisflies exhibited a dose response to salt treatments with 96-h LC50 values of 7700 and 3526 mg NaCl/l, respectively. Most other invertebrate species and individuals were unaffected by NaCl concentrations up to 10,000 mg/l for 24 and 96 h, respectively.     

Alphafetoprotein,cholinesterases and rapidly adhering cells in the prenatal diagnosis of neural tube defects

Amniotic fluid cholinesterases tested on polyacrylamide gel and rapidly adhering cell analysis were compared in their efficiency at diagnosing fetal neural tube defects in three cases where the alphafetoprotein results were equivocal. While rapidly adhering cells were also equivocal, the cholinesterases consistently gave a clear indication of fetal abnormality.     

Application of a cave inventory system to stimulate development of management strategies: the case of west-central Florida, USA

The active management of air-filled cave systems is virtually non-existent within the karst landscape of west-central Florida. As in every karst landscape, caves are important because they contain a wide variety of resources (e.g., biota, speleothems) and can act as direct connections between surface and subsurface hydrological processes, potentially exacerbating the pollution of groundwater. Before sound management policies can be drafted, implemented, and enforced, stakeholders must first have knowledge of the management requirements of each cave. However, there is an informational disconnect between researchers, stakeholders, and the recreational caving community. Here, we present a cave inventory system that simplifies the dissemination of resource knowledge to stakeholders so that cave management and protection policies can be drafted and implemented at the state and local level. We inventoried 36 caves in west-central Florida, located on both public and private land, and analyzed cave resource data to provide insights on cave sensitivity and disturbance using two standardized indices. The data revealed that both public and private caves exhibit a wide range of sensitivity and disturbance, and before management strategies can be drafted, the ownership of each cave must be considered. Our inventory geodatabase serves as a link between researchers, landowners, and the public. To ensure the conservation and protection of caves, support from county or state government, combined with cave inventory data, is crucial in developing sound management policy.