Fabric filters versus electrostatic precipitators

Control of particulate emissions from pulverized coal fired steam generators is becoming a significant factor in the siting and public acceptability of large coal burning power plants. The particulate emission limit established by the EPA for new coal fired boilers is 0.03 lb/10⁶ Btu (13 ng/J) Possibly more restrictive than this is the state of New Mexico's particulate regulation which calls for no more than 0.05 lb/10⁶ Btu (22 ng/J) total, and no more than 0.02 lb/10⁶ Btu (9 ng/J) less than 2 microns in diameter. This paper will evaluate the effect of these stringent limitations on the technical feasibility and economics of dry particulate removal. Electrostatic precipitators have been the dominant particulate collection device in the electric utility industry for many years because of their low capital and operating cost. However, increasingly stringent emission standards have led to substantially higher costs for precipitators. These costs have increased sufficiently for fabric filtration to become a competitive alternative in achieving cost effective control. This paper will compare the economics and performance of fabric filtration with respect to conventional electrostatic precipitators. The paper will also address the preliminary evaluation procedures that should be followed in order to select the appropriate device for new or existing coal-fired boilers.     

N-nitrosodimethylamine in drinking water using a rapid,solid-phase extraction method

A simple, rapid method for the extraction of N-nitrosodimethylamine (NDMA) from drinking and surface waters was developed using Ambersorb 572. Development of an alternative method to classical liquid-liquid extraction techniques was necessary to handle the workload presented by implementation of a provincial guideline of 9 ppt for drinking water and a regulatory level of 200 ppt for effluents. A granular adsorbent, Ambersorb 572, was used to extract the NDMA from the water in the sample bottle. The NDMA was extracted from the Ambersorb 572 with dichloromethane in the autosampler vial. Method characteristics include a precision of 4 % for replicate analyses, an accuracy of 6 % at 10 ppt and a detection limit of 1.0 ppt NDMA in water. Comparative data between the Ambersorb 572 method and liquid-liquid extraction showed excellent agreement (average difference of 12 %). With the Ambersorb 572 method, dichloromethane use has been reduced by a factor of 1,000 and productivity has been increased by a factor of 3–4. Monitoring of a drinking water supply showed rapidly changing concentrations of NDMA from day to day.     

Teaching Approaches in Geography and Students’ Environmental Attitudes

In a study which examines the pattern of geography teaching at the Advanced Level in Hong Kong and assesses the relative effectiveness of didactic and enquiry teaching approaches that are used by the teachers concerned for the development of positive values towards the environment, the question was asked as to whether or not enquiry is more effective than didactic approaches for the development of environmental values, in both the short and long terms, for students as a whole and for students from different ability ranges. Questionnaire surveys and interviews were conducted to obtain data from students after they were taught a topic on people and the environment in the curriculum, with the approach chosen by their teachers. Results show that the enquiry approach was effective with the lower to medium ability classes in the short term but students who were taught didactically performed better in more areas in the longer term. The possible causes for this pattern are discussed and suggestions for improving the effectiveness of enquiry approaches in a high-pressure, examination-oriented classroom environment are offered.     

TREE‐RING BASED RECONSTRUCTIONS OF INTERANNUAL TO DECADAL SCALE PRECIPITATION VARIABILITY FOR NORTHEASTERN UTAH SINCE 1226 A.D.1

ABSTRACT: Samples from 107 piñon pines (Pinns edulis) at four sites were used to develop a proxy record of annual (June to June) precipitation spanning the 1226 to 2001 AD interval for the Uinta Basin Watershed of northeastern Utah. The reconstruction reveals significant precipitation variability at interannual to decadal scales. Single‐year dry events before the instrumental period tended to be more severe than those after 1900. In general, decadal scale dry events were longer and more severe prior to 1900. In particular, dry events in the late 13th, 16th, and 18th Centuries surpass the magnitude and duration of droughts seen in the Uinta Basin after 1900. The last four decades of the 20th Century also represent one of the wettest periods in the reconstruction. The proxy record indicates that the instrumental record (approximately 1900 to the Present) underestimates the potential frequency and severity of severe, sustained droughts in this area, while over representing the prominence of wet episodes. In the longer record, the empirical probability of any decadal scale drought exceeding the duration of the 1954 through 1964 drought is 94 percent, while the probability for any wet event exceeding the duration of the 1965 through 1999 wet spell is only 1 percent. Hence, estimates of future water availability in the Uinta Basin and forecasts for exports to the Colorado River, based on the 1961 to 1990 and 1971 to 2000 “normal” periods, may be overly optimistic.     

Unit costs for decontamination and dismantlement of structures

A series of relationships have been developed for estimating unit costs for decontamination and dismantlement (D&D) of a number of structure types. These relationships may be applied in the absence of other data to obtain rough order-of-magnitude cost estimates for D&D activities. The relationships were developed using D&D costs estimated for various types of buildings at the U.S. Department of Energy Fernald site. These unit costs take into account the level of radiological contamination as well as the building size and type.     

New directions in Mexican environmental policy

Since taking office 1 December 1988, Mexico's incumbent president, Carlos Salinas de Gortari, has introduced important innovations in environmental policy that distinguish his administration from those of his predecessors. Greater administrative continuity, improved regulatory capacity achieved through statutory change, focused priorities centering on pollution abatement in Mexico City, and an aggressive search for external financing for pollution control are hallmarks of Salinas' approach. The success of these environmental reforms depends heavily on economic recovery, however, and environmental policy still suffers from underfunding, bureaucratic fragmentation, and heavy reliance on voluntarist enforcement mechanisms. Recently, U.S. congressional debate on a proposed free trade agreement with Mexico has been a factor in spurring the Salinas government to take new antipollution and conservation measures. Mexico's growing environmental movement is also an important force behind the government's new responsiveness in environmental matters. The Salinas administration recognizes the issue's political salience and has sought to defuse environmental criticism using a large arsenal of resources at its disposal. Salinas' environmental policy strategy may thus be characterized as both proactive and reactive in nature. While the reforms are evidence that Mexico is beginning to take environmental matters more seriously, economic recovery and sustained environmental activism remain vital to further progress.     

The contribution of energy efficiency to sustainable development in developing countries

The demand for energy services is growing rapidly in developing countries. Low levels of energy efficiency in electric power supply and in energy use mean that the energy sector threatens to absorb an intolerably high share of available financial resources. Energy inefficiency also contributes to local and global environmental problems. A strategy of vigorously improving energy efficiency is thus a key element of a sustainable development path. Results reported in this paper show that there is considerable room for efficiency improvement in both existing and new capital stocks, but a much larger effort than presently underway is essential if the potential is to be realized. Assistance from the industrialized countries can play a major role in such an effort.     

Survey of water use behaviour in rural North Ghana

Evaluation research of rural water projects has not paid much attention to examining the extent to which intended beneficiaries actually utilized the new water points for drinking purposes. This paper presents a survey of water use patterns in a rural district of Ghana to find out the source(s) of water for drinking both at home and when on the farm. Because farms are at a considerable distance from the settlements where the boreholes are located, the use of borehole water when on the farm provides a good standard with which to evaluate community education components of the water programmes.     

Measuring environmental success

Process improvement, environmental results, and customer satisfaction all can—and need to—be measured in order to achieve total quality environmental management. This article details why and how to take such measures, with examples of leading company practices.