Visualization and optimization of cavitation activity at a solid surface in high frequency ultrasound fields.

Despite the increasing use of high frequency ultrasound in heterogeneous reactions, knowledge about the spatial distribution of cavitation bubbles at the irradiated solid surface is still lacking. This gap hinders controllable surface sonoreactions. Here we present an optimization study of the cavitation bubble distribution at a solid sample using sonoluminescence and sonochemiluminescence imaging. The experiments were performed at three ultrasound frequencies, namely 580, 860 and 1142kHz. We found that position and orientation of the sample to the transducer, as well as its material properties influence the distribution of active cavitation bubbles at the sample surface in the reactor. The reason is a significant modification of the acoustic field due to reflections and absorption of the ultrasonic wave by the solid. This is retraced by numerical simulations employing the Finite Element Method, yielding reasonable agreement of luminescent zones and high acoustic pressure amplitudes in 2D simulations. A homogeneous coverage of the test sample surface with cavitation is finally reached at nearly vertical inclination with respect to the incident wave.

A national investigation of the prevalence and diversity of thermophilic Campylobacter species in agricultural watersheds in Canada.

The occurrence and diversity of thermophilic Campylobacter species (C. jejuni, coli, and lari) were studied in water samples from four river basins located across Canada. These basins located in Quebec (Bras d'Henri), Alberta (Oldman), Ontario (South Nation), and British Columbia (Sumas) represented some of the most intensive farming areas in Canada for hog, beef cattle, dairy cattle, and poultry, respectively. This study analyzed 769 water samples collected from 23 monitoring sites with agricultural influence, and four reference sites with limited or no agricultural influence. Water samples were collected bi-weekly over two years and analyzed for Campylobacter using a semi-quantitative minimum probable number (MPN) enrichment protocol. Putative isolates were confirmed by genus- and species-specific multiplex polymerase chain reaction (PCR) assays. A total of 377 (49%) water samples were positive for campylobacters with 355 samples having a cell density ranging from 4 to 4000 MPN L(-1). Campylobacters were more common at agricultural than reference sites in each river basin, although this difference was not significant in the Oldman and South Nation (p > 0.05). Campylobacter was significantly more common in the Bras d'Henri and Sumas (63%) compared to the South Nation (45%) and Oldman (33%) River basins (p < 0.05). C. jejuni, C. coli and C. lari were detected in each river basin, and these species occurred in 45% (n = 168), 34% (n = 128) and 19% (n = 73), of all Campylobacter positive samples, respectively. The remaining Campylobacter positive water samples without these three species (n = 67; 18%) were identified as other Campylobacter species. C. jejuni was the predominant species occurring in the Sumas, Oldman and South Nation River basins. However, in the Bras d'Henri River basin with intensive hog production, C. coli was the predominant species. This study found campylobacters to be common in some agricultural systems with intensive livestock farming activities, and different river basins could have strikingly different profiles of either C. jejuni or C. coli as the predominant waterborne thermophilic Campylobacter species.

Assessment of Giardia and Cryptosporidium spp. as a microbial source tracking tool for surface water: application in a mixed-use watershed.

Knowledge of host specificity, combined with genomic sequencing of Giardia and Cryptosporidium spp., has demonstrated a microbial source tracking (MST) utility for these common waterborne microbes. To explore the source attribution potential of these pathogens, water samples were collected in a mixed rural-urban watershed in the Township of Langley, in southwestern British Columbia (BC), Canada, over a 2-year period. Cryptosporidium was detected in 63% of surface water samples at concentrations ranging from no positive detection (NPD) to 20,600 oocysts per 100 liters. Giardia was detected in 86% of surface water samples at concentrations ranging from NPD to 3,800 cysts per 100 liters of water. Sequencing at the 18S rRNA locus revealed that 50% of Cryptosporidium samples and 98% of Giardia samples contained species/genotypes (Cryptosporidium) or assemblages (Giardia) that are capable of infecting humans, based on current knowledge of host specificity and taxonomy. Cryptosporidium genotyping data were more promising for source tracking potential, due to the greater number of host-adapted (i.e., narrow-host-range) species/genotypes compared to Giardia, since 98% of Giardia isolates were zoonotic and the potential host could not be predicted. This report highlights the benefits of parasite genomic sequencing to complement Method 1623 (U.S. Environmental Protection Agency) and shows that Cryptosporidium subtyping for MST purposes is superior to the use of Giardia subtyping, based on better detection limits for Cryptosporidium-positive samples than for Giardia-positive samples and on greater host specificity among Cryptosporidium species. These additional tools could be used for risk assessment in public health and watershed management decisions.

A framework for assessing cumulative effects in watersheds: an introduction to Canadian case studies.

From 2008 to 2013, a series of studies supported by the Canadian Water Network were conducted in Canadian watersheds in an effort to improve methods to assess cumulative effects. These studies fit under a common framework for watershed cumulative effects assessment (CEA). This article presents an introduction to the Special Series on Watershed CEA in IEAM including the framework and its impetus, a brief introduction to each of the articles in the series, challenges, and a path forward. The framework includes a regional water monitoring program that produces 3 core outputs: an accumulated state assessment, stressor-response relationships, and development of predictive cumulative effects scenario models. The framework considers core values, indicators, thresholds, and use of consistent terminology. It emphasizes that CEA requires 2 components, accumulated state quantification and predictive scenario forecasting. It recognizes both of these components must be supported by a regional, multiscale monitoring program.

Water and sewage systems, socio-demographics, and duration of residence associated with endemic intestinal infectious diseases: a cohort study.

BACKGROUND: Studies of water-related gastrointestinal infections are usually directed at outbreaks. Few have examined endemic illness or compared rates across different water supply and sewage disposal systems. We conducted a cohort study of physician visits and hospitalizations for endemic intestinal infectious diseases in a mixed rural and urban community near Vancouver, Canada, with varied and well-characterized water and sewage systems. METHODS: Cohort members and their disease events were defined via universal health insurance data from 1995 through 2003. Environmental data were derived from municipal, provincial, and federal government sources. Logistic regression was used to examine associations between disease events and water and sewage systems, socio-demographic characteristics, and temporal factors. RESULTS: The cohort included 126,499 individuals and approximately 190,000,000 person-days. Crude incidence rates were 1,353 physician visits and 33.8 hospitalizations for intestinal infectious diseases per 100,000 person-years. Water supply chlorination was associated with reduced physician visit incidence (OR: 0.92, 95% CI 0.85-1.0). Two water systems with the highest proportions of surface water had increased incidence (ORs: 1.57, 95% CI 1.39-1.78; and 1.45, 95% CI 1.28-1.64). Private well water and well depth were not associated with increased risk, likely because of residents' awareness of and attention to water quality. There was increased crude incidence with increasing precipitation in the population served by surface water supplies, but this trend did not remain with adjustment for other variables. Municipal sewer systems were associated with increased risk (OR: 1.26, 95% CI 1.14-1.38). Most socio-demographic variables had predicted associations with risk: higher rates in females, in the very young and the elderly, and in residents of low income areas. Increased duration of area residence was associated with reduced risk (OR, duration ≥ 6 years: 0.69, 95% CI 0.60-0.80 vs. < 1 year: 1.16, 95% CI 1.03-1.30). CONCLUSIONS: This large cohort study, with objective data on exposures and outcomes, demonstrated associations between endemic infectious intestinal diseases and factors related to water supply, sewage disposal, socio-demographics, and duration of residency. The results did not always follow prior expectations based on studies examining outbreaks and single systems, and underscore the importance of studying factors associated with endemic disease across water and sewage system types.

The occurrence and sources of Campylobacter spp., Salmonella enterica and Escherichia coli O157:H7 in the Salmon River, British Columbia, Canada.

In this study, we wished to assess the prevalence and determine the sources of three zoonotic bacterial pathogens (Salmonella, Campylobacter, and Escherichia coli O157:H7) in the Salmon River watershed in southwestern British Columbia. Surface water, sewage, and animal faecal samples were collected from the watershed. Selective bacterial culture and PCR techniques were used to isolate these three pathogens and indicator bacteria from these samples and characterize them. Campylobacter was the most prevalent pathogen in all samples, followed by Salmonella, and E. coli O157:H7. E. coli O157:H7 and Salmonella isolation rates from water, as well as faecal coliform densities correlated positively with precipitation, while Campylobacter isolation rates correlated negatively with precipitation. Analysis of DNA extracted from water samples for the presence of Bacteroides host-species markers, and comparisons of C. jejuni flaA-RFLP types and Salmonella serovars from faecal and water samples provided evidence that human sewage and specific domestic and wild animal species were sources of these pathogens; however, in most cases the source could not be determined or more than one source was possible. The frequent isolation of these zoonotic pathogens in the Salmon River highlights the risks to human health associated with intentional and unintentional consumption of untreated surface waters.

A methods comparison for the isolation and detection of thermophilic Campylobacter in agricultural watersheds.

Campylobacter species contribute to an enormous burden of enteric illnesses around the world. This study compared two different methods for detecting Campylobacter species in surface water samples from agricultural watersheds across Canada. One method was based on membrane filtration (MF) of 500 ml water samples followed by selective microaerophilic enrichment at 42 degrees C in Bolton broth, isolation of Campylobacter on CCDA, and subsequent identification confirmation by a PCR assay. The second method was based on centrifugation (CF) of 1000 ml water samples, followed by selective microaerophilic enrichment at 42 degrees C in Bolton broth, isolation of Campylobacter on Modified Karmali Agar, and subsequent identification confirmation by a different PCR assay. Overall comparison of the CF and MF methods indicated that both methods found Camylobacterjejuni to be the most commonly detected Campylobacter species in 699 water samples from four agricultural watersheds across Canada, and that C. jejuni frequency of occurrence was similar by both methods. However, the CF method detected significantly higher frequencies of Campylobactercoli (17%) and other Campylobacter species (13%) than the MF method (11% and 3%, respectively). It was frequently found that one method would detect Campylobacter in a water sample when the other method would not for a simultaneously collected, duplicate water sample. This study indicates that methods can have significantly different recovery efficiencies for Campylobacter species, and that caution is needed when comparing studies that report on the frequency of occurrence of waterborne Campylobacter at the genus level when different detection methods are used.

Microwave pretreatment for enhancement of phosphorus release from dairy manure.

Both the advanced oxidation process (AOP) using a combination of hydrogen peroxide addition and microwave heating (H2O2/microwave), and the microwave heating process were used for solubilization of phosphorus from liquid dairy manure. About 80% of total phosphate was released into the solution at a microwave heating time of 5 min at 170 degrees C. With an addition of H2O2, more than 81% of total phosphate could be released over a reaction period of 49 h at ambient temperature. The AOP process could achieve up to 85% of total phosphate release at 120 degrees C. The results indicated that both the microwave, and the AOP processes could effectively release phosphate from liquid dairy manure. These processes could serve as pretreatments for phosphorus recovery from animal wastes, and could be combined with the struvite crystallization process to provide a new approach in treating animal wastes.

Aerosolization of lipoplexes using AERx Pulmonary Delivery System.

The lung represents an attractive target for delivering gene therapy to achieve local and potentially systemic delivery of gene products. The objective of this study was to evaluate the feasibility of the AERx Pulmonary Delivery System for delivering nonviral gene therapy formulations to the lung. We found that "naked" DNA undergoes degradation following aerosolization through the AERx nozzle system. However, DNA formulated with a molar excess of cationic lipids (lipoplexes) showed no loss of integrity. In addition, the lipoplexes showed no significant change in particle size, zeta (zeta) potential, or degree of complexation following extrusion. The data suggest that complexation with cationic lipids had a protective effect on the formulation following extrusion. In addition, there was no significant change in the potency of the formulation as determined by a transfection study in A-549 cells in culture. We also found that DNA formulations prepared in lactose were aerosolized poorly. Significant improvements in aerosolization efficiency were seen when electrolytes such as NaCl were added to the formulation. In conclusion, the data suggest that delivery of lipoplexes using the AERx Pulmonary Delivery System may be a viable approach for pulmonary gene therapy.