Leigh-Anne Krometis

Child dysentery in the Limpopo Valley: a cohort study of water, sanitation and hygiene risk factors

The objective of this cohort study was to assess risk factors for child dysentery and watery diarrhoea. The study participants consisted of 254 children aged 12-24 months in rural South Africa and Zimbabwe in households where drinking water was collected from communal sources. The main outcome measure was the most severe diarrhoea episode: dysentery, watery diarrhoea or none. For dysentery, drinking water from sources other than standpipes had a relative risk ratio of 3.8 (95% CI 1.5-9.8). Poor source water quality, as indicated by Escherichia coli counts of 10 or more cfu 100 ml(-1), increased risk by 2.9 (1.5-5.7). There were no other significant risk factors for dysentery and none for watery diarrhoea. In this study, endemic dysentery is associated only with faecal contamination of source water. Sources other than standpipes, including improved groundwater, are of greater risk. Remediation of water quality by treatment at source or in the household will be required to achieve access to safe drinking water in accordance with the 7th Millennium Development Goal.The appropriateness of indicator organisms as surrogates for human pathogens in water quality modeling is dependent on similarities in both presence and transport behavior; however, very little data relating indicator and bacterial pathogen transport behavior in receiving waters is available. In this study observations of presence, partitioning behavior (i.e. association with settleable particles) and removal by upland detention basins were used to assess the suitability of six indicator organisms as surrogates for Salmonella spp. bacteria in an urban watershed. The fecal indicator bacteria (fecal coliforms, E. coli and enterococci) were most closely correlated with Salmonella in terms of presence and partitioning behavior (25-35% associated with settleable particles on average); however, further resolution of the variability associated with Salmonella partitioning is required. Higher removal of particle-associated microbes relative to the total microbial concentration by the detention ponds suggests that sedimentation may be an important removal mechanism. However, large fluctuations in pond performance between storm events and occasional net microbial exports in effluents indicate that these best management practices (BMPs), as currently implemented, will be unlikely to achieve water quality objectives.

The “Death” of Disciplines: Development of a Team-Taught Course to Provide an Interdisciplinary Perspective for First-Year Students

Although interdisciplinary efforts in teaching and research are promoted as a possible antidote to increasing disciplinary separatism in colleges and universities, evaluations of interdisciplinary efforts in the classroom, particularly those spanning the traditional science-humanities divide, are not frequently documented. This article describes the development, execution, and assessment of a unique effort in interdisciplinary teaching in which four doctoral candidates from widely varying home disciplines collaborated to create and teach a “truly interdisciplinary” course for first-year students centered on the pervasiveness of humankinds quest for immortality. Assessment of the course indicates several desirable student outcomes, including the development of a more mature world view and appreciation for different epistemologies, which recommend the continuation of this and similar interdisciplinary efforts. While students at times found the enormous number of disciplines potentially related to the central topic overwhelming, at the conclusion of the course, they largely identified the exposure to new perspectives as an exciting and worthwhile academic experience. Similar interdisciplinary efforts in the classroom are encouraged, though ample course development time is recommended to maximize success.

Impact of microbial partitioning on wet retention pond effectiveness.

Wet detention basins are among the most common best management practices (BMPs) being implemented as means of complying with United States Phase II storm-water rules and impending Total Maximum Daily Load limits. The effectiveness of these basins for removal of microbial contaminants, one of the most frequent causes of water quality impairment, may be significantly affected by the degree to which microbes associate with particles in storm water. Little is known with regard to where microbial-particle associations are initiated within the storm-water transport chain as flow travels from upland sources (e.g., lawns, parking lots) through storm sewer systems and BMPs and finally on to receiving waters. A similar lack of information exists on the relative concentrations of microbes at each point in the transport chain. Both of these factors have important implications for the location of wet detention basins within a watershed, as well as their anticipated effectiveness. This study tracked the concentrations ...

Identification of Particle Size Classes Inhibiting Protozoan Recovery from Surface Water Samples via U.S. Environmental Protection Agency Method 1623

ABSTRACT Giardia species recovery by U.S. Environmental Protection Agency method 1623 appears significantly impacted by a wide size range (2 to 30 μm) of particles in water and organic matter. Cryptosporidium species recovery seems negatively correlated only with smaller (2 to 10 μm), presumably inorganic particles. Results suggest constituents and mechanisms interfering with method performance may differ by protozoan type.

Incidence of waterborne lead in private drinking water systems in Virginia

Although recent studies suggest contamination by bacteria and nitrate in private drinking water systems is of increasing concern, data describing contaminants associated with the corrosion of onsite plumbing are scarce. This study reports on the analysis of 2,146 samples submitted by private system homeowners. Almost 20% of first draw samples submitted contained lead concentrations above the United States Environmental Protection Agency action level of 15 μg/L, suggesting that corrosion may be a significant public health problem. Correlations between lead, copper, and zinc suggested brass components as a likely lead source, and dug/bored wells had significantly higher lead concentrations as compared to drilled wells. A random subset of samples selected to quantify particulate lead indicated that, on average, 47% of lead in the first draws was in the particulate form, although the occurrence was highly variable. While flushing the tap reduced lead below 15 μg/L for most systems, some systems experienced an increase, perhaps attributable to particulate lead or lead-bearing components upstream of the faucet (e.g., valves, pumps). Results suggest that without including a focus on private as well as municipal systems it will be very difficult to meet the existing national public health goal to eliminate elevated blood lead levels in children.

Assessing the Effects of Climate Change on Waterborne Microorganisms: Implications for EU and U.S. Water Policy

ABSTRACT Despite advances in water treatment, outbreaks of waterborne diseases still occur in developed regions including the United States and Europe Union (EU). Water quality impairments attributable to elevated concentrations of fecal indicator bacteria, and associated with health risk, are also very common. Research suggests that the impact of such microorganisms on public health may be intensified by the effects of climate change. At present, the major regulatory frameworks in these regions (i.e., the US Clean Water Act [CWA] and the EU Water Framework Directive [WFD]), do not explicitly address risks posed by climate change. This article reviews existing U.S. and EU water quality regulatory legislation for robustness to climate change and suggests watershed modeling approaches to inform additional pollution control measures given the likely impacts on microbial fate and transport. Comprehensive analysis of future climate and water quality scenarios may only be achievable through the use of watershed-scale models. Unless adaptation measures are generated and incorporated into water policy, the potential threat posed to humans from exposure to waterborne pathogens may be amplified. Such adaptation measures will assist in achieving the aims of the EU WFD and US CWA and minimize impacts of climate change on microbial water quality.

Quantitative analysis of microbial contamination in private drinking water supply systems

Over one million households rely on private water supplies (e.g. well, spring, cistern) in the Commonwealth of Virginia, USA. The present study tested 538 private wells and springs in 20 Virginia counties for total coliforms (TCs) and Escherichia coli along with a suite of chemical contaminants. A logistic regression analysis was used to investigate potential correlations between TC contamination and chemical parameters (e.g. NO3(-), turbidity), as well as homeowner-provided survey data describing system characteristics and perceived water quality. Of the 538 samples collected, 41% (n = 221) were positive for TCs and 10% (n = 53) for E. coli. Chemical parameters were not statistically predictive of microbial contamination. Well depth, water treatment, and farm location proximate to the water supply were factors in a regression model that predicted presence/absence of TCs with 74% accuracy. Microbial and chemical source tracking techniques (Bacteroides gene Bac32F and HF183 detection via polymerase chain reaction and optical brightener detection via fluorometry) identified four samples as likely contaminated with human wastewater.

Applications of Microbial Source Tracking in the TMDL Process

The US Environmental Protection Agency’s Total Maximum Daily Load (TMDL) program is frequently cited as a primary driver in the development of microbial source tracking (MST) techniques. As MST techniques continue to mature, it is prudent to identify those areas where further MST-related research is most likely to contribute to the efficient development and implementation of bacterial TMDLs. The objectives of this chapter are to review the basic phases in the TMDL process, to describe current applications of MST within these stages, to identify research needed to increase MST application, and to discuss opportunities for the expanded use of MST data within the TMDL process.

Storm loads of culturable and molecular fecal indicators in an inland urban stream.

Elevated concentrations of fecal indicator bacteria in receiving waters during wet-weather flows are a considerable public health concern that is likely to be exacerbated by future climate change and urbanization. Knowledge of factors driving the fate and transport of fecal indicator bacteria in stormwater is limited, and even less is known about molecular fecal indicators, which may eventually supplant traditional culturable indicators. In this study, concentrations and loading rates of both culturable and molecular fecal indicators were quantified throughout six storm events in an instrumented inland urban stream. While both concentrations and loading rates of each fecal indicator increased rapidly during the rising limb of the storm hydrographs, it is the loading rates rather than instantaneous concentrations that provide a better estimate of transport through the stream during the entire storm. Concentrations of general fecal indicators (both culturable and molecular) correlated most highly with each other during storm events but not with the human-associated HF183 Bacteroides marker. Event loads of general fecal indicators most strongly correlated with total runoff volume, maximum discharge, and maximum turbidity, while event loads of HF183 most strongly correlated with the time to peak flow in a hydrograph. These observations suggest that collection of multiple samples during a storm event is critical for accurate predictions of fecal indicator loading rates and total loads during wet-weather flows, which are required for effective watershed management. In addition, existing predictive models based on general fecal indicators may not be sufficient to predict source-specific genetic markers of fecal contamination.

Hydrometeorological and Physicochemical Drivers of Fecal Indicator Bacteria in Urban Stream Bottom Sediments

High levels of fecal indicator bacteria (FIB) are the leading cause of surface water quality impairments in the United States. Watershed-scale models are commonly used to identify relative contributions of watershed sources and to evaluate the effectiveness of remediation strategies. However, most existing models simplify FIB transport behavior as equivalent to that of dissolved-phase contaminants, ignoring the impacts of sediment on the fate and transport of FIB. Implementation of sediment-related processes within existing models is limited by minimal available monitoring data on sediment FIB concentrations for model development, calibration, and validation purposes. The purpose of the present study is to evaluate FIB levels in the streambed sediments as compared to those in the water column and to identify environmental variables that influence water and underlying sediment FIB levels. Concentrations of and enterococci in the water column and sediments of an urban stream were monitored weekly for 1 yr and correlated with a variety of potential hydrometeorological and physicochemical variables. Increased FIB concentrations in both the water column and sediments were most strongly correlated with increased antecedent 24-h rainfall, increased stream water temperature, decreased dissolved oxygen, and decreased specific conductivity. These observations will support future efforts to incorporate sediment-related processes in existing models through the identification of key FIB relationships with other model inputs, and the provision of sediment FIB concentrations for direct model calibration. In addition, identified key variables can be used in quick evaluation of the effectiveness of potential remediation strategies.