The thief process for mercury removal from flue gas

The Thief Process is a cost-effective variation to activated carbon injection (ACI) for removal of mercury from flue gas. In this scheme, partially combusted coal from the furnace of a pulverized coal power generation plant is extracted by a lance and then re-injected into the ductwork downstream of the air preheater. Recent results on a 500-lb/h pilot-scale combustion facility show similar removals of mercury for both the Thief Process and ACI. The tests conducted to date at laboratory, bench, and pilot-scales demonstrate that the Thief sorbents exhibit capacities for mercury from flue gas streams that are comparable to those exhibited by commercially available activated carbons. A patent for the process was issued in February 2003. The Thief sorbents are cheaper than commercially-available activated carbons; exhibit excellent capacities for mercury; and the overall process holds great potential for reducing the cost of mercury removal from flue gas. The Thief Process was licensed to Mobotec USA, Inc. in May of 2005.     

Demography of Two Mexican Spotted Owl Populations

Abstract: The Mexican Spotted Owl ( Strix occidentalis lucida ) is a threatened subspecies of the southwestern United States and northern Mexico. Although threatened, little is known about its population status. We studied the demography of the Mexican Spotted Owl in one study area in Arizona and one in New Mexico from 1991 to 1997. We estimated annual survival rates (φ), fecundity rates (   b ), and abundance (   N ) to test the hypothesis that population trends were stationary. Although annual fecundity rates (   b ^ = 0.494 for Arizona and 0.380 for New Mexico) and annual juvenile survival rates ( φ^ = 0.179 for Arizona and 0.109 for New Mexico) differed in magnitude between the study areas, they exhibited similar temporal patterns. Annual survival for territorial owls varied randomly in Arizona but declined linearly in New Mexico. Mean annual survival for territorial owls was 0.814 in Arizona and 0.832 for owls ≥3 years old and 0.644 for owls 1–2 years old in New Mexico. Based on survival and fecundity estimates, the annual rates of change (λ^) indicated that both populations were declining at ≥10% a year. These estimates were corroborated by observed declines in abundance. Some regional factor may have been affecting fecundity, whereas a combination of factors may have been affecting survival. Two possible reasons for the population declines are declines in habitat quality and regional trends in climate.     

EQUILIBRIUM EVAPORATION AND POSITWE EVAPORATION-SURFACE TEMPERATURE RELATIONSHIPS ACROSS A GRASSLAND1

Sensible (H) and latent (LE) heat fluxes, soil moisture (SM) and surface temperatures (T_s) were analyzed from seven sites at FIFE to evaluate relationships among the spatial variability of evaporative fraction, EF, SM, and the diurnal surface temperature range (T_dr). Intersite correlations between EF and T_dr were significantly negative for regional average soil moisture SM_r < 20 percent, insignificant for 20 < SM_r < 27 percent, and slightly positive for SM_r > 27 percent. Statistical analysis of the pooled correlation coefficient between EF and T_dr for SM_r < 20 percent indicates that it is less than zero at a very high level of significance, while the pooled correlation coefficient for regional SM_r > 27 percent is greater than zero at the 10 percent level. The positive EF:T_dr correlations are attributed to increased surface vapor pressure at warmer sites under nearly potential conditions. These results suggest that to characterize the spatial variability of the energy budget partitioning, a variable representing the thermal response of the site should be included. An important application of these findings relates to modeling the subgrid variability of a region by subdividing the region into a few classes within which surface variables and parameters are assumed invariant. The thermal response of the surface should be included as a variable in defining these classes.     

Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds1

Watson, Tara K., Dorothy Q. Kellogg, Kelly Addy, Arthur J. Gold, Mark H. Stolt, Sean W. Donohue, and Peter M. Groffman, 2010. Groundwater Denitrification Capacity of Riparian Zones in Suburban and Agricultural Watersheds. Journal of the American Water Resources Association (JAWRA) 46(2):237-245. DOI: 10.1111/j.1752-1688.2010.00418.x Abstract: We evaluated the relationship of dominant watershed land use to the structure and nitrogen (N) sink function of riparian zones. We focused on groundwater denitrification capacity, water table dynamics, and the presence and pattern of organically enriched deposits. We used the push-pull method (measurement of ¹⁵N-enriched denitrification gases derived from an introduced groundwater plume of ¹⁵N-enriched nitrate) to evaluate groundwater denitrification capacity on nine forested wetland riparian sites developed in alluvial or outwash parent materials in southern New England. Three replicate sites were located in each of the three watershed types, those with substantial (1) irrigated agriculture, (2) suburban development, and (3) forest. Soil morphology and water table dynamics were assessed at each site. We found significantly lower mean annual water tables at sites within watersheds with substantial irrigated agriculture or suburban development than forested watersheds. Water table dynamics were more variable at sites within suburban watersheds, especially during the summer. Groundwater denitrification capacity was significantly greater at sites within forested watersheds than in watersheds with substantial irrigated agriculture. Because of the high degree of variability observed in riparian sites within suburban watersheds, groundwater denitrification capacity was not significantly different from either forested or agricultural watersheds. The highly variable patterns of organically enriched deposits and water tables at sites within suburban watersheds suggests that depositional events are irregular, limiting the predictability of groundwater N dynamics in these riparian zones. The variability of riparian N removal in watersheds with extensive suburbia or irrigated agriculture argues for N management strategies emphasizing effective N source controls in these settings.     

Remediation of MTBE-Contaminated Water and Soil

As the number of leaking underground fuel tank sites with methyl tertiary butyl ehter (MTBE) contamination continues to grow, there is a need to develop cost-effective solutions for treatment of soil and water contamination. MTBE poses special challenges because of its physicochemical properties, in particular high solubility and low Henry's constant, low affinity for sorption, and very slow rate of microbial degradation. Advanced oxidation processes tend to generate undesirable by-products. Based on laboratory studies with hollow fiber membranes (HFM), a field-scale unit was constructed and tested at a number of sites, to determine the effectiveness of this technology in dealing with MTBE contamination. In addition, to treat the soil contamination, the HFM unit was coupled with a Spray Aeration Vapor Extraction (SAVE) unit, which is based on an internal combustion engine. The engine provides the means to treat soil vapors, as well as organic vapors from the spray aeration and HFM units. The overall treatment objectives of 5μg/l for MTBE and 1 μg/l for benzene were achieved with a treatment train consisting of an ion exchange unit, a spray aeration system, a hollow fiber membrane module and two granular activated carbon (GAC) units, for flowrates ranging from 3.8 to 30 l/min (1 to 8 gal/min). The ion exchange unit sewed to reduce water hardness and avoid scaling in the subsequent treatment units, extending the run-time of the entire system. Overall removal efficiencies for the spray aeration system and hollow fiber membrane module ranged from 85 to over 99 percent. High removal efficiencies (> 97%) were obtained at elevated water temperatures (54°C) or lower flowrates (up to 11 l/min). The GAC units were used only to polish the effluent and meet the discharge requirements. Soil, water, and gas phases are treated with this system. Cost estimates are provided for similar treatment processes, for water flowrates up to 38 l/min (10 gal/min). © 1999 John Wiley & Sons, Inc.