Drained response of municipal solid waste in large-scale triaxial shear testing

A comprehensive laboratory investigation was performed on municipal solid waste (MSW) from a landfill located in northern California using a large-scale triaxial (TX) apparatus. An improved, standardized waste specimen preparation method was developed and used to prepare 27 large-scale TX specimens (d=300mm, h=600-630mm). The effects of waste composition, confining stress, unit weight, loading rate, and stress path on the drained stress-strain response of MSW were investigated. Waste composition has a significant effect on its stress-strain response. The commonly observed upward curvature of the stress-strain response of specimens composed of larger-sized waste materials results from the fibrous constituents (primarily paper, plastic and wood) reinforcing the waste matrix. This effect is greatest when the MSW specimen is sheared across the long axis of the fibrous particles. Due to this significant strain hardening effect and waste's in situ stress state, a limiting strain failure criterion of 5% axial strain from the K(o) field consolidation state is judged to be most appropriate. Results from this test program and data from the literature indicate that the TX compression secant friction angle of MSW varies from 34° to 44°, with 39° as a best estimate, at a confining stress of one atmosphere (assuming c=0). The friction angle decreases as confining stress increases. The friction angles measured in this testing program are representative of failure surfaces that are oriented at an angle to the predominant orientation of the long axis of the fibrous waste particles. These friction angles are higher than those obtained in direct shear tests where shearing typically occurs parallel to the orientation of the fibrous waste particles.     

Analysis of the relationship between ambient levels of O3, NO2 and NO as a function of NOx in the UK

Monitoring data from the UK Automatic Urban and Rural Network are used to investigate the relationships between ambient levels of ozone (O₃), nitric oxide (NO) and nitrogen dioxide (NO₂) as a function of NO_x, for levels ranging from those typical of UK rural sites to those observed at polluted urban kerbside sites. Particular emphasis is placed on establishing how the level of ‘oxidant’, OX (taken to be the sum of O₃ and NO₂) varies with the level of NO_x, and therefore to gain some insight into the atmospheric sources of OX, particularly at polluted urban locations. The analyses indicate that the level of OX at a given location is made up of NO_x-independent and NO_x-dependent contributions. The former is effectively a regional contribution which equates to the regional background O₃ level, whereas the latter is effectively a local contribution which correlates with the level of primary pollution. The local oxidant source has probable contributions from (i) direct NO₂ emissions, (ii) the thermal reaction of NO with O₂ at high NO_x, and (iii) common-source emission of species which promote NO to NO₂ conversion. The final category may include nitrous acid (HONO), which appears to be emitted directly in vehicle exhaust, and is potentially photolysed to generate HO_x radicals on a short timescale throughout the year at southern UK latitudes. The analyses also show that the local oxidant source has significant site-to-site variations, and possible reasons for these variations are discussed. Relationships between OX and NO_x, based on annual mean data, and fitted functions describing the relative contributions to OX made by NO₂ and O₃, are used to define expressions which describe the likely variation of annual mean NO₂ as a function of NO_x at 14 urban and suburban sites, and which can take account of possible changes in the regional background of O₃.     

GIS‐BASED HYIROLOGIC MODELING OF RIPARIAN AREAS: IMPLICATIONS FOR STREAM WATER QUALITY1

ABSTRACT: Riparian buffers have potential for reducing excess nutrient levels in surface water. Spatial variation in riparian buffer effectiveness is well recognized, yet researchers and managers still lack effective general tools for understanding the relevance of different hydrologic settings. We present several terrain‐based GIS models to predict spatial patterns of shallow, subsurface hydrologic flux and riparian hydrology. We then link predictions of riparian hydrology to patterns of nutrient export in order to demonstrate potential for augmenting the predictive power of land use/land cover (LU/LC) maps. Using predicted hydrology in addition to LUILC, we observed increases in the explained variation of nutrient exports from 290 sites across Lower Michigan. The results suggest that our hydrologic predictions relate more strongly to patterns of nutrient export than the presence or absence of wetland vegetation, and that in fact the influence of vegetative structure largely depends on its hydrologic context. Such GIS models are useful and complimentary tools for exploring the role of hydrologic routing in riparian ecosystem function and stream water quality. Modeling efforts that take a similar GIS approach to material transport might be used to further explore the causal implications of riparian buffers in heterogeneous watersheds.     

A SPATIAL LINEAR PROGRAM FOR OPTIMALLY SCHEDULING FOREST MANAGEMENT TO MEET STORMFLOW OBJECTWES1

ABSTRACT: A spatial linear program that strategically arranges and schedules forest treatments so as to meet peak stormflow objectives is formulated and demonstrated. The approach uses simulated spatial routing of stormflows nested as short‐term time schedules within longer‐term forest planning time periods. A simple case example is used to demonstrate the formulation and explore its spatial sensitivity.     

Treatment of Highly Contaminated Groundwater: A SITE Demonstration Project

From September through November 1994, the U.S. Environmental Protection Agency (EPA) conducted a field demonstration of the remediation of highly contaminated groundwater at the Nascolite Superfund site located in Millville, New Jersey. Besides high concentrations of the major contaminant, methyl methacrylate (MMA), the groundwater also contained small amounts of volatile and semivolatile organic compounds. ZenoGem® technology, an integrated bioreactor and ultrafiltration membrane system, was employed for this demonstration project. Approximately 30,000 gallons of groundwater containing MMA in concentrations of 567 to 9,500 milligrams per liter (mg/L) and chemical oxygen demand (COD) values ranging from 1,490 to 19,600 mg/L was treated. The demonstration focused on the system's ability to remove MMA and reduce COD from the groundwater. Results of the three‐month demonstration showed that average MMA and COD removal efficiencies were greater than 99.9 and 86.9, respectively. The total cost of treatment, depending on the duration of the project, is estimated to vary from $0.22 to $0.55 (in 1994 dollars) per gallon of groundwater treated. © 2001 John Wiley & Sons.     

Cellobiose dehydrogenase-dependent biodegradation of polyacrylate polymers by Phanerochaete chrysosporium

When Phanerochaete chrysosporium was cultured using conditions which promote the expression of cellobiose dehydrogenase (CDH), but not the ligninolytic peroxidases, the fungus effectively solubilized and mineralized an insoluble, crosslinked polyacrylate and an insoluble polyacrylate/polyacrylamide copolymer. Addition of iron to the cultures increased CDH activity in the cultures and the rate and extent of solubilization and mineralization of both polymers. Solubilization of both polymers was observed when incubated with purified CDH, ferric iron and hydrogen peroxide.     

Neighborhood quality in environmentally stressed areas of Accra, Ghana: a comparison with US counterparts

A sample of 873 residents of Accra, Ghana, stratified by type of neighborhood was gathered in order to measure the association of poor neighborhood quality with neighborhood problems and residents' personal characteristics. Strong associations were found with poor schools, physical blight, rowdy and criminal behavior, ethnic differences, and environmental problems. In addition, poor neighborhood quality was strongly associated with mistrust of authority and a feeling of a lack of control over neighborhood activities. Respondents identified road, street, drainage, sewage, and other infrastructure deficiencies as priorities to address, even though these were not prominent discriminators of neighborhood quality ratings. Many of these findings are common to counterparts in the US, but some findings appear to reflect cultural and differences in urbanization.     

ENHANCEMENTS OF NONPOINT SOURCE MONITORING OF VOLATILE ORGANIC COMPOUNDS IN GROUND WATER1

ABSTRACT: The U.S. Geological Survey (USGS) has compiled a national retrospective data set of analyses of volatile organic compounds (VOCs) in ground water of the United States. The data are from Federal, State, and local nonpoint‐source monitoring programs, collected between 1985–95. This data set is being used to augment data collected by the USGS National Water‐Quality Assessment (NAWQA) Program to ascertain the occurrence of VOCs in ground water nationwide. Eleven attributes of the retrospective data set were evaluated to determine the suitability of the data to augment NAWQA data in answering occurrence questions of varying complexity. These 11 attributes are the VOC analyte list and the associated reporting levels for each VOC, well type, well‐casing material, type of openings in the interval (screened interval or open hole), well depth, depth to the top and bottom of the open interval(s), depth to water level in the well, aquifer type (confined or unconfined), and aquifer lithology. VOCs frequently analyzed included solvents, industrial reagents, and refrigerants, but other VOCs of current interest were not frequently analyzed. About 70 percent of the sampled wells have the type of well documented in the data set, and about 74 percent have well depth documented. However, the data set generally lacks documentation of other characteristics, such as well‐casing material, information about the screened or open interval(s), depth to water level in the well, and aquifer type and lithology. For example, only about 20 percent of the wells include information on depth to water level in the well and only about 14 percent of the wells include information about aquifer type. The three most important enhancements to VOC data collected in nonpoint‐source monitoring programs for use in a national assessment of VOC occurrence in ground water would be an expanded VOC analyte list, recording the reporting level for each analyte for every analysis, and recording key ancillary information about each well. These enhancements would greatly increase the usefulness of VOC data in addressing complex occurrence questions, such as those that seek to explain the reasons for VOC occurrence and nonoccurrence in ground water of the United States.     

Aerobic Cometabolism of Halogenated Aliphatic Hydrocarbons: A Technology Overview

Bioremediation of chlorinated solvents has been moving from an innovative to mainstream technology for environmental applications. Cometablism of chlorinated solvents by monooxygenase has been demonstrated for trichloroethylene (TCE). Cl‐out microbes combine the dehalogenation of PCE with the monooxygenase destruction of TCE to complete the PCE breakdown pathway. Underthe right conditions, cometabolic bioremediation can be cost effective, fast, and complete. Aerobic bioremediation can augment mass transfer technologies such as pump and treat or sparging/vapor extraction to improve their efficiency.