DIE‐OFF OF PATHOGENIC E. COLI O157:H7 IN SEWAGE CONTAMINATED WATERS1

E. coli O157:H7 is a pathogen that can be present in sewage contaminated waters. This organism poses a health risk for humans who come in contact with these waters via drinking, swimming, or shellfish consumption. A risk assessment model is needed to evaluate or quantify this risk. One possibility is the use of a computer model to simulate the fate and transport of E. coli O157:H7 downstream from a discharge point [e.g., a separate sanitary sewer overflow (SSO)]. However, this computer model would require input data regarding characteristics of this organism, which have not been previously available. One necessary input parameter is the rate at which die off of this organism occurs in a stream or river environment. Several studies were conducted to evaluate the die‐off rate of E. coli O157:H7 in an SSO impacted stream. Indicator bacteria (total coliforms, E. coli, and enterococci) were evaluated simultaneously. The results suggest that E. coli O157:H7 is not persistent — decay rates are high relative to the indicator bacteria. However, the decay plots suggest a biphasic response: initial decay is rapid, followed by an attenuated, slower decay. Hence traditional simulation methods using a single, first‐order decay rate may be inaccurate.     

Remedial options for chlorinated volatile organics in a partially anaerobic aquifer

A laboratory study was conducted for the selection of appropriate remedial technologies for a partially anaerobic aquifer contaminated with chlorinated volatile organics (VOCs). Evaluation of in situ bioremediation demonstrated that the addition of electron donors to anaerobic microcosms enhanced biological reductive dechlorination of tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1‐trichloroethane (1,1,1‐TCA) with half‐lives of 20, 22, and 41 days, respectively. Nearly complete reductions of PCE, TCE, 1,1,1‐TCA, and the derivative cis‐dichloroethene were accompanied by a corresponding increase in chloride concentrations. Accumulation of vinyl chloride, ethene, and ethane was not observed; however, elevated levels of ¹⁴CO₂ (from ¹⁴C‐TCE spiked) were recovered, indicating the occurrence of anaerobic oxidation. In contrast, very little degradation of 1,2‐dichloropropane (1,2‐DCP) and 1,1‐dichlorethane (1,1‐DCA) was observed in the anaerobic microcosms, but nutrient addition enhanced their degradation in the aerobic biotic microcosms. The aerobic degradation half‐lives for 1,2‐DCP and 1,1‐DCA were 63 and 56 days, respectively. Evaluation of in situ chemical oxidation (ISCO) demonstrated that chelate‐modified Fenton's reagent was effective in degrading aqueous‐phase PCE, TCE, 1,1,1‐TCA, 1,2‐DCP, etc.; however, this approach had minimal effects on solid‐phase contaminants. The observed oxidant demand was 16 g‐H₂O₂/L‐groundwater. The oxidation reaction rates were not highly sensitive to the molar ratio of H₂O₂:Fe²⁺:citrate. A ratio of 60:1:1 resulted in slightly faster removal of chemicals of concern (COCs) than those of 12:1:1 and 300:1:1. This treatment resulted in increases in dissolved metals (Ca, Cr, Mg, K, and Mn) and a minor increase of vinyl chloride. Treatment with zero‐valent iron (ZVI) resulted in complete dechlorination of PCE, and TCE to ethene and ethane. ZVI treatment reduced 1,1,1‐TCA only to 1,1‐DCA and chloroethane (CA) but had little effect on reducing the levels of 1,2‐DCP, 1,1‐DCA, and CA. The longevity test showed that one gram of 325‐mesh iron powder was exhausted in reaction with > 22 mL of groundwater. The short life of ZVI may be a barrier to implementation. The ZVI surface reaction rates (k_sa) were 1.2 × 10^?2 Lm^?2h^?1, 2 × 10^?3 Lm^?2h^?1, and 1.2 × 10^?3 Lm^?2h^?1 for 1,1,1‐TCA, TCE, and PCE, respectively. Based upon the results of this study, in situ bioremediation appeared to be more suitable than ISCO and ZVI for effectively treating the groundwater contamination at the site. © 2004 Wiley Periodicals, Inc.     

Measurement of transferable chemical residue from nylon carpet using the California roller and a new mega-California roller

Human chemical exposures resulting from transfer of surface deposition on indoor nylon carpets may be estimated by measuring transferable residues (mu g chemical/cm2 carpet). A weighted roller developed at California Department of Food and Agriculture (CDFA) has been extensively used to sample transferable residue for estimates of human exposure in risk characterization. A modified roller has been developed to evaluate the influence of pressure on transferable chemical residue since weight and force (or pressure, kg/m2) may vary person-to-person and activity-to-activity. A 30.5 cm diameter roller was used to apply 60 to 2100 kg/m2 to bracket pressures exerted by humans on a flat nylon-carpeted surface. Measurements of transferable cyfluthrin residues were made after 1, 7, and 21 days. Total Soxhlet extractable cyfluthrin residues were relatively constant during the test period. Residue transferability decreased during the study period. Modest increases in the transferability of surface residues were observed over the broad range of pressures applied by the modified roller.     

Why not in your backyard? scientific data and nonrational decisions about risk

The siting of hazardous waste facilities constitutes a special case of the many no win environmental decisions we face. They share common features: (a) we must decide something; (b) the decision affects some people more than others; (c) as scientists we are not 100% confident of our research results; (d) elements of the decision remain unquantifiable; and (e) decisions combine both scientific and political elements. In this paper we attempt to illustrate and analyze several examples that combine all of these elements and to suggest methods which would lead toward a scientific valid and politically useful resolution. Using well-known examples such as the public's fear of death from nuclear power, snakebite, and smoking, we attempt to integrate public perception of risks into a decision-making model. Finally, the conclusions deal with the role of policy making, public perception, and science in resolving environmental controversies. We do not, however, solve this perplexing problem.     

Local Cultural Knowledge and Water Resource Management: The Wind River Indian Reservation

Ecology and culture comprise interacting components of landscapes. Understanding the integrative nature of the landscape is essential to establish methods for sustainable management. This research takes as a unifying theme the idea that ecological and cultural issues can be incorporated through management. As a first step in developing integrative management strategies, information must be collected that compares and contrasts ecological and cultural issues to identify their areas of intersection. Specifically how can local cultural knowledge enable water resource management that reflects cultural and ecological values? This research examines Native American cultural knowledge for setting water resource management priorities in the Wind River Indian Reservation in central Wyoming. A cross-cultural approach is adopted to assess the relationship between indigenous cultural knowledge and Euro-American perspectives through a comparative examination of the Wind River Water Code and Wyoming Water Law. This research indicates that cultural perspectives provide a rich arena in which to examine management issues. Understanding and identifying cultural practices may be an important first step in collaborative resource management between different cultural groups to prevent conflict and lengthy resolution in court.     

Valuing externalities from water supply: Status quo,choice complexity and individual random effects in panel kernel logit analysis of choice experiments

Choice experiments are often implemented with choice sets including one alternative depicting the status quo. Utility from status quo is experienced by the respondent, while utility associated with experimentally designed hypothetical alternatives is only conjectured by respondents. The effects of explicitly accounting for such a difference in the econometric analysis of the data are often unreported, or limited to fitting a ‘status quo’ constant. The paper proposes a model that explicitly accounts for these effects and attempts their decomposition using data from two choice modelling exercises designed to value the provision of environmental goods. Preferences for change versus status quo are explored with standard specifications along with a less usually applied error component analysis via mixed logit. The results suggest that alternatives offering changes from status quo do not share the same preference structure as the status quo alternative, and that estimates of spread parameters in zero-mean error components can be decomposed conditional on respondents' socio-economic characteristics. It is argued that these findings have implications for practitioners and their stance towards the strategies for the econometric analysis of choice modelling data for the purpose of valuation.     

Trihalomethane formation during water disinfection in four water supplies in the Somes river basin in Romania

Background, aim and scope  

After the discovery of chloroform in drinking water, an extensive amount of work has been dedicated to the factors influencing the formation of halogenated disinfections by-products (DBPs). The disinfection practice can vary significantly from one country to another. Whereas no disinfectant is added to many water supplies in Switzerland or no disinfectant residual is maintained in the distribution system, high disinfectant doses are applied together with high residual concentrations in the distribution system in other countries such as the USA or some southern European countries and Romania. In the present study, several treatment plants in the Somes river basin in Romania were investigated with regard to chlorine practice and DBP formation (trihalomethanes (THMs)). Laboratory kinetic studies were also performed to investigate whether there is a relationship between raw water dissolved organic matter, residual chlorine, water temperature and THM formation.     

Escaping to and being active in neighbourhood parks: park use in a post-disaster setting

Neighbourhood parks may serve as a coping resource in post-disaster communities, yet little is known about the impact of large-scale disasters on park use. The objective of this study is to explore the impact of Hurricane Katrina (August 2005) on park use by visitors from flooded areas of New Orleans, Louisiana, compared to visitors from non-flooded areas. In 2006 and 2007, following Hurricane Katrina, 201 adults who visited 27 New Orleans parks were interviewed. Visitors from flooded neighbourhoods used their parks less often and were less likely to engage in animal interaction than visitors from non-flooded neighbourhoods. They placed more importance on escape and physically-active motivations than visitors from non-flooded areas. Social reasons were also more important to visitors from flooded areas, but these differences disappeared after adjusting for race. Neighbourhood parks are a community asset that may play a role in the post-disaster recovery process by providing opportunities for escape and physical activity.