Inactivation of particle-associated viral surrogates by ultraviolet light

This study investigated whether colloid-sized particles can enmesh and protect viruses from 254-nm ultraviolet (UV) light and sought to determine the particle characteristics (e.g. size, chemical composition) that are most relevant in causing a protective effect. Two viral surrogates (MS2 coliphage and bacteriophage T4), three types of particles (kaolin clay, humic acid powder, and activated sludge), two coagulants (alum and ferric chloride), two filtration conditions (none and 0.45 microm), and two UV doses (40 and 80 mJ/cm2 for MS2 coliphage; 2 and 7 mJ/cm2 for bacteriophage T4) were considered in a series of bench-scale UV collimated beam experiments. Transmission electron microscopy was used to qualitatively confirm the phage particle-association after coagulation. Humic acid and activated sludge floc particles shielded both viral surrogates to a statistically significant degree (with >99% confidence) relative to particle-free control conditions, while the kaolin clay particles provided no significant protection. The results of the study suggest that particles <2 microm in diameter are large enough to protect viruses from UV light and that particulate chemical composition (e.g. UV-absorbing organic content) may be a critical factor in the survival of particle-associated viruses during UV disinfection.     

The effect of surroundings with different separation distances on surface pressures on low-rise buildings

Very large roof suctions on low-rise buildings occur for isolated buildings during both full-scale experiments and wind tunnel tests performed by many investigators. This paper investigates the sensitivity of these high suctions to the presence of multiple surrounding building configurations. This study uses the Wind Engineering Research Field Laboratory (WERFL) building studied during the CSU/TTU Cooperative Program in Wind Engineering as a basic building shape. A model of the WERFL structure was constructed to a 1:50 scale and instrumented with multiple pressure ports. Pressure taps on the 1:50 scale building model were connected to two 48-channel PSI transducer units. A large number of “dummy” models of similar dimensions were constructed to represent surrounding buildings. These model buildings were arranged in various symmetric configurations with different separation distances, and placed in the Industrial Wind Tunnel of the Wind Engineering and Fluids Laboratory, Colorado State University. Measurements include mean, RMS and peak pressures, street canyon velocity profiles and laser-sheet flow visualizations. Shelter effects produced by the surrounding buildings on the central instrumented building were found to be significant, such that flow patterns are displaced and mean and peak induced loads are significantly different from the isolated building base case. The surface pressures of master WERFL model inside the urban street canyons were determined by the prognostic model FLUENT using the four differences closure approximation and FDS, large eddy simulations methodology. Calculations are compared against fluid modeling from wind-tunnel test.     

Stimulating the anaerobic biodegradation of explosives by the addition of hydrogen or electron donors that produce hydrogen

The anaerobic biodegradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 2,4,6-trinitrotoluene (TNT) by a methanogenic mixed culture was investigated. Microcosms containing a basal medium and the mixed culture were amended with ethanol, propylene glycol (PG), butyrate or hydrogen gas as the electron donor and a mixture of TNT (50 microM), RDX (25 microM), and HMX (8 microM). After 29 days TNT and RDX were completely transformed to unidentified endproducts in the bottles amended with ethanol, hydrogen, or PG, while 53%, 40%, and 22% of the HMX was transformed, respectively. There was no loss of RDX or HMX in the electron donor unamended control bottles. The ethanol and PG were transformed to near stoichiometric amounts of acetate and propionate, suggesting the immediate electron donor supporting the transformation of the explosives was the H2 evolved during the metabolism of the parent substrate. Our findings suggest that the addition of H2 or electron donors that produce H2 may be a useful strategy for enhancing the anaerobic biodegradation of explosives in contaminated groundwater and soils.     

A FRAMEWORK FOR CLIMATE RISK MANAGEMENT APPLIED TO A UK WATER RESOURCE PROBLEM

Climate risk management is a new and evolving area and many decisions are likely to be affected by climate risks over the long-term. This paper presents a decision-making framework designed for managing climate alongside nonclimate risk factors. The framework describes a process that should help identify and manage these risks. It can be used to help decision-makers answer questions about whether adaptation is required, and, if so, which measures should be implemented. Adaptive management is recommended as a useful approach for dealing with climate and other uncertainties. This paper describes an application of the framework to a water resources case study. Feedback from training workshops based on four different case studies suggests the framework provides at minimum a useful (post-hoc) decision analysis tool. Potential users, who include planners, consultants and policy-makers have been largely positive about the prospective utility of the framework.     

Arsenic removal by iron-modified activated carbon

Iron-impregnated activated carbons have been found to be very effective in arsenic removal. Oxyanionic arsenic species such as arsenate and arsenite adsorb at the iron oxyhydroxide surface by forming complexes with the surface sites. Our goal has been to load as much iron within the carbon pores as possible while also rendering as much of the iron to be available for sorbing arsenic. Surface oxidation of carbon by HNO3/H2SO4 or by HNO3/KMnO4 increased the amount of iron that could be loaded to 7.6-8.0%; arsenic stayed below 10 ppb until 12,000 bed volumes during rapid small-scale tests (RSSCTs) using Rutland, MA groundwater (40-60 ppb arsenic, and pH of 7.6-8.0). Boehm titrations showed that surface oxidation greatly increased the concentration of carboxylic and phenolic surface groups. Iron impregnation by precipitation or iron salt evaporation was also evaluated. Iron content was increased to 9-17% with internal iron-loading, and to 33.6% with both internal and external iron loading. These iron-tailored carbons reached 25,000-34,000 bed volumes to 10 ppb arsenic breakthrough during RSSCTs. With the 33.6% iron loading, some iron peeled off.     

Innovation in urban systems: The interrelationships between urban and national economic development

The theoretical basis for analysing the role of innovation in economic development is assessed, as is the application of such theories to urbanisation processes. It is concluded that innovation lies at the heart of economic development and that urban development has important feedback effects on national economic development. Analysing these feedbacks requires a sophisticated data set allowing the analysis of input-output relationships in urban systems over time. In the absence of such data, industry employment classifications are used as a proxy for economic structure in an analysis of United States and Australian cities. Particular kinds of cities in the urban hierarchy can be analysed in terms of their economic structure and this can then be related to national economic development trends. The contributions of categories of city (particularly by size class) to economic development can then be explored. Obviously, results will vary with the era of economic development covered by the data. However, in all eras, certain kinds of cities will emerge as leaders in the process of urban economic development and will also play a crucial role in national economic development.     

Biophysical processes and bioregional planning: The Niagara Escarpment of southern Ontario, Canada

The Niagara Escarpment is the dominant landscape feature of Southern Ontario and has been designated a UNESCO World Biosphere Reserve. As with many such natural features, the resource planning and management strategies developed tend to be based upon the present-day situation rather than upon a recognition of the changing and evolving nature of the feature. To develop strategies incorporating change demands that a knowledge be gained of the processes operating in those components of the ecosystems in which measurable activity will take place within a planning framework; that is a timescale of several decades. In this particular case, the context is natural resource planning for the scarp face itself. The critical system elements are those related to earth surface processes, forest ecosystem dynamics, and in particular, their interrelationships. Different planning objectives require information at differing spatial scales. Yet these objectives must be related, whether they are local site-specific issues, or are related to the maintenance of the biodiversity of the whole 725 km of the Escarpment. One way to achieve these goals is to establish a hierarchical system of spatially nested land units. These units, however, must be based on the underlying biophysical processes responsible for the dynamics in any one of these spatially determined frameworks. In this case, the underlying biophysical processes relating to geomorphology and forest ecosystem dynamics are found to be influenced by one of three dominant slope forms. The recurrence of these slope forms throughout the Escarpment then permits 9 distinct regional land units to be identified. Within these units, site-specific analysis examines earth surface/forest interactions and change. Subsequently, from these site specific analyses data are accumulated to develop a more general model of earth surface/forest ecosystem interaction for the Escarpment as a whole.     

New suburban centers: An Australian perspective

Suburban “edge cities” are an international phenomenon registering the impacts of a growing global economy, the increasing footlooseness of capital, advances in communication technology, the growth of hi-tech industry, and the forces of decentralisation. Yet they do assume culturally specific forms. Using the case study of North Ryde in the Sydney metropolitan area, differences between Australia and the United States in terms of the dynamism and scale of their respective edge-city environments are highlighted. Four explanatory factors are identified: the comparative nature of the Australian economy, the differential strength of planning controls, contrasting central city—suburban relationships, and a lesser degree of freeway dependence.     

An examination of the mechanisms for stable foam formation in activated sludge systems

Screening pure cultures of 65 mycolic acid producing bacteria (Mycolata) isolated mainly from activated sludge with a laboratory based foaming test revealed that not all foamed under the conditions used. However, for most, the data were generally consistent with the flotation theory as an explanation for foaming. Thus a stable foam required three components, air bubbles, surfactants and hydrophobic cells. With non-hydrophobic cells, an unstable foam was generated, and in the absence of surfactants, cells formed a greasy surface scum. Addition of surfactant converted a scumming population into one forming a stable foam. The ability to generate a foam depended on a threshold cell number, which varied between individual isolates and reduced markedly in the presence of surfactant. Consequently, the concept of a universal threshold applicable to all foaming Mycolata is not supported by these data. The role of surfactants in foaming is poorly understood, but evidence is presented for the first time that surfactin synthesised by Bacillus subtilis may be important.     

Growth and control of filamentous microbes in activated sludge: an integrated hypothesis

Since its initial development and application, the activated sludge process has undergone a continual evolution aimed at maximizing process efficiency and controlling population selection. Organic loading rate, dissolved oxygen concentration and reactor configuration have been implicated as key process variables affecting sludge settleability, their combined effects determining which microbe or microbes are best able to grow and survive in a given system. Using available pure and mixed culture observations, a conceptual hypothesis centered around three model organisms has been developed to explain the growth and control of filamentous organisms in activated sludge. Organism selection in continuously fed systems has been hypothesized to be dominated by filamentous organisms with high sustainable growth rates at low reactor substrate concentrations/organic loading rates and filaments best able to compete for dissolved oxygen at elevated reactor substrate concentrations/organic loading rates. Intermittently fed systems, on the other hand, enrich for nonfilamentous organisms which both rapidly extract substrate from solution and maintain peak activity during extended periods of endogeneous metabolism. While both types of reactor induced feeding patterns can control filamentous organism growth, intermittently fed systems are capable of operation over a wider range of operating conditions by accentuating differences in organism physiology. Additional selection pressures such as substrate composition, non-ideal reactor hydraulics and time-variable influent waste streams were also discussed in relation to their impact on idealized systems.