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Municipal stormwater systems are designed to collect, transport, and discharge precipitation from a defined catchment area into local surface waters. However, these discharges may contain unsafe levels of fecal waste. Paired measurements of Escherichia coli, precipitation, three land use metrics determined by geographic information system (GIS) mapping, and host-associated genetic markers indicative of human (HF183/BacR287 and HumM2), ruminant (Rum2Bac), dog (DG3), and avian (GFD) fecal sources were assessed in 231 urban stream samples impacted by two or more municipal stormwater outfalls. Receiving water samples were collected twice per month (n = 24) and after rain events (n = 9) from seven headwaters of the Anacostia River in the District of Columbia (United States) exhibiting a gradient of impervious surface, residential, and park surface areas. Almost 50% of stream samples (n = 103) were impaired, exceeding the local E. coli single sample maximum assessment level (410 MPN/100 ml). Fecal scores (average log10 copies per 100 ml) were determined to prioritize sites by pollution source and to evaluate potential links with land use, rainfall, and E. coli levels using a recently developed censored data analysis approach. Dog, ruminant, and avian fecal scores were almost always significantly increased after rain or when E. coli levels exceeded the local benchmark. Human fecal pollution trends showed the greatest variability with detections ranging from 9.1% to 96.7% across sites. Avian fecal scores exhibited the closest connection to land use, significantly increasing in catchments with larger residential areas after rain events (p = 0.038; R2 = 0.62). Overall, results demonstrate that combining genetic fecal source identification methods with GIS mapping complements routine E. coli monitoring to improve management of urban streams impacted by stormwater outfalls. [ABSTRACT FROM AUTHOR]

Fecal pollution management remains one of the biggest challenges for water quality authorities worldwide. Advanced fecal pollution source identification technologies are now available that can provide quantitative information from many animal groups. As public interest in these methodologies grows, it is vital to use standardized procedures with clearly defined data acceptance metrics and conduct field studies demonstrating the use of these techniques to help resolve real-world water quality challenges. Here we apply recently standardized human-associated qPCR methods with custom data acceptance metrics (HF183/BacR287 and HumM2), along with established procedures for ruminant (Rum2Bac), cattle (CowM2 and CowM3), canine (DG3 and DG37), and avian (GFD) fecal pollution sources to (i) demonstrate the feasibility of implementing standardized qPCR procedures in a large-scale field study, and (ii) characterize trends in fecal pollution sources in the research area. A total of 602 water samples were collected over a one-year period at 29 sites along the Trask, Kilchis, and Tillamook rivers and tributaries in the Tillamook Bay Watershed (OR, USA). Host-associated qPCR results were combined with high-resolution geographic information system (GIS) land use and general indicator bacteria (E. coli) measurements to elucidate water quality fecal pollution trends. Results demonstrate the feasibility of implementing standardized fecal source identification qPCR methods with established data acceptance metrics in a large-scale field study leading to new investigative leads suggesting that elevated E. coli levels may be linked to specific pollution sources and land use activities in the Tillamook Bay Watershed. [ABSTRACT FROM AUTHOR]

Summary Genetic markers from Bacteroides and other faecal bacteria are being tested for inclusion in regulations to quantify aquatic faecal contamination and estimate public health risk. For the method to be used quantitatively across environments, persistence and decay of markers must be understood. We measured concentrations of contaminant molecular markers targeting Enterococcus and Bacteroides spp. in marine and freshwater microcosms spiked with human sewage and exposed to either sunlight or dark treatments. We used Bayesian statistics with a delayed Chick-Watson model to estimate kinetic parameters for target decay. DNA- and RNA-based targets decayed at approximately the same rate. Molecular markers persisted (could be detected) longer in marine water. Sunlight increased the decay rates of cultured indicators more than those of molecular markers; sunlight also limited persistence of molecular markers. Within each treatment, Bacteroides markers had similar decay profiles, but some Bacteroides markers significantly differed in decay rates. The role of extracellular DNA in persistence appeared unimportant in the microcosms. Because conditions were controlled, microcosms allowed the effects of specific environmental variables on marker persistence and decay to be measured. While marker decay profiles in more complex environments would be expected to vary from those observed here, the differences we measured suggest that water matrix is an important factor affecting quantitative source tracking and microbial risk assessment applications. [ABSTRACT FROM AUTHOR]

Two bacteriophages, ϕ6 and ϕ8, were investigated as potential surrogates for H5N1 highly pathogenic avian influenza virus in persistence and chlorine inactivation studies in water. In the persistence studies, ϕ6 and ϕ8 remained infectious at least as long as the H5N1 viruses at both 17 and 28°C in fresh water, but results varied in salinated water. The bacteriophage ϕ6 also exhibited a slightly higher chlorine resistance than that of the H5N1 viruses. Based upon these findings, the bacteriophages may have potential for use as surrogates in persistence and inactivation studies in fresh water. [ABSTRACT FROM AUTHOR]

Adverse health effects that may result from chronic exposure to mixtures of disinfection by-products (DBPs) present in drinking waters may be linked to both the types and concentrations of DBPs present. Depending on the characteristics of the source water and treatment processes used, both types and concentrations of DBPs found in drinking waters vary substantially. The composition of a drinking-water mixture also may change during distribution. This study evaluated the relationships between mutagenicity, using the Ames assay, and water quality parameters. The study included information on treatment, mutagenicity data, and water quality data for source waters, finished waters, and distribution samples collected from five full-scale drinking water treatment plants, which used chlorine exclusively for disinfection. Four of the plants used surface water sources and the fifth plant used groundwater. Correlations between mutagenicity and water quality parameters are presented. The highest correlation was observed between mutagenicity and the total organic halide concentrations in the treated samples. [ABSTRACT FROM AUTHOR]

The objective of this study was to measure hydroxyl radical reaction rates using both UV/H[sub2]O[sub2] and pulse radiolysis techniques for 10 US EPA Contaminant Candidate List compounds (2,6- and 2,4-DNT, EPTC, prometon, linuron, diuron, RDX, molinate, nitrobenzene, and terbacil). The rate constants determined using these techniques were compared to each other and to values reported in the literature. Difference factors between k[subOH] obtained using UV/H[sub2]O[sub2] and pulse radiolysis ranged from 1.1 to 4.7. It was shown that even small differences in hydroxyl radical rate constants values can result in fairly large differences (up to 50%) when trying to predict removals of pollutants in an advanced oxidation process. [ABSTRACT FROM AUTHOR]

Background: In real-time quantitative PCR studies using absolute plasmid DNA standards, a calibration curve is developed to estimate an unknown DNA concentration. However, potential differences in the amplification performance of plasmid DNA compared to genomic DNA standards are often ignored in calibration calculations and in some cases impossible to characterize. A flexible statistical method that can account for uncertainty between plasmid and genomic DNA targets, replicate testing, and experiment-to-experiment variability is needed to estimate calibration curve parameters such as intercept and slope. Here we report the use of a Bayesian approach to generate calibration curves for the enumeration of target DNA from genomic DNA samples using absolute plasmid DNA standards. Results: Instead of the two traditional methods (classical and inverse), a Monte Carlo Markov Chain (MCMC) estimation was used to generate single, master, and modified calibration curves. The mean and the percentiles of the posterior distribution were used as point and interval estimates of unknown parameters such as intercepts, slopes and DNA concentrations. The software WinBUGS was used to perform all simulations and to generate the posterior distributions of all the unknown parameters of interest. Conclusion: The Bayesian approach defined in this study allowed for the estimation of DNA concentrations from environmental samples using absolute standard curves generated by real-time qPCR. The approach accounted for uncertainty from multiple sources such as experiment-to-experiment variation, variability between replicate measurements, as well as uncertainty introduced when employing calibration curves generated from absolute plasmid DNA standards. [ABSTRACT FROM AUTHOR]

The U.S. Environmental Protection Agency currently recommends Ct (disinfectant concentration multiplied by the exposure time) values to achieve required levels of inactivation of Giardia lamblia cysts by different disinfectants including free chlorine. Current guidance covers inactivation levels in the pH range between 6 and 9. Subsequent to the publication of these criteria, studies on the inactivation kinetics of Giardia cysts by chlorine have been performed at pH levels greater than 9. It has been shown that the chlorine inactivation process for Giardia cysts is pH dependent. The objective of this paper is to extend the current Ct values for higher pH levels. The Chick-Watson first order kinetics model was used to develop Ct values for pH levels from 6 to 11.5. A formula is provided to calculate a 100(1 - α)% upper confidence bound for these values. [ABSTRACT FROM AUTHOR]

A major challenge for society in the 21st century will be replacement, design, and optimal management of urban infrastructure. It is estimated that the current worldwide demand for infrastructure investment is approximately three trillion dollars annually. A Drinking Water Infrastructure Needs Survey conducted by the U.S. Environmental Protection Agency estimated that community water systems nationwide have an immediate need of $12.1 billion in infrastructure investment, primarily to protect against microbiological contamination. This paper presents equations that can be used to estimate the cost of system construction, expansion, and rehabilitation and repair for distribution system components. Equations have been developed for installation of new pipe, trenching, embedment, and the other unit operations that are required to replace or construct new distribution system components. Equations have also been developed to estimate the cost of cement mortar lining, sliplining, and corrosion control. These equations can be used in an additive manner to estimate the cost of all of the unit operations required for replacing or laying new distribution system piping, and for a limited set of rehabilitation and repair options. [ABSTRACT FROM AUTHOR]

There is growing concern over the need to rehabilitate, replace, and repair drinking water distribution systems and wastewater collection systems in the United States. A recent survey conducted by the U.S. Environmental Protection Agency found that $138 billion will be needed to maintain and replace existing drinking water systems over the next 20 years. It is estimated that $77 billion of this expenditure will be dedicated to repairing and rehabilitating pipelines. Given the cost and disruption caused by replacing distribution system pipe using conventional open trench technology, utilities are beginning to increase the application of rehabilitation or trenchless replacement technologies to extend the life of existing pipes. This paper discusses the various types of technologies that can be used for rehabilitation and repair of drinking water distribution components. It also presents representative costs that can be used by utility managers to estimate order-of-magnitude budgetary costs for rehabilitation and replacement of distribution system components. [ABSTRACT FROM AUTHOR]

Reviews research efforts related to the development of models for predicting chlorine decay as of March 2002. Major objective of drinking water treatment; Categories of reactions that occur between organic compounds and chlorine species; Factors that influence the demand for chlorine; Constituents in water that react with chlorine.

Develops a mathematical model based on a set of variables to predict the formation of total trihalomethanes and brominated by-products in drinking water. Factors that influence the formation of disinfection by-products; Development of the model; Model validation and model interpretation.

Presents a model that predicts both total trihalomethanes (TTHM) and chlorine residuals based on the consumption of chlorine. Experimental design; Developing a predictive equation; Validation of predictive models; Conclusion.

To determine resistance of highly pathogenic avian influenza (H5N1) virus to chlorination, we exposed allantoic fluid containing 2 virus strains to chlorinated buffer at pH 7 and 8, at 5 degrees C. Free chlorine concentrations typically used in drinking water treatment are sufficient to inactivate the virus by >3 orders of magnitude. [ABSTRACT FROM AUTHOR]

Draft method C is a standardized method for quantifying E. coli densities in recreational waters using quantitative polymerase chain reaction (qPCR). The method includes a Microsoft Excel workbook that automatically screens for poor-quality data using a set of previously proposed acceptance criteria, generates weighted linear regression (WLR) composite standard curves, and calculates E. coli target gene copies in test samples. We compared standard curve parameter values and test sample results calculated with the WLR model to those from a Bayesian master standard curve (MSC) model using data from a previous multi-lab study. The two models' mean intercept and slope estimates from twenty labs' standard curves were within each other's 95% credible or confidence intervals for all labs. E. coli gene copy estimates of six water samples analyzed by eight labs were highly overlapping among labs when quantified with the WLR and MSC models. Finally, we compared multiple labs' 2016–2018 composite curves, comprised of data from individual curves where acceptance criteria were not used, to their corresponding composite curves with passing acceptance criteria. Composite curves developed from passing individual curves had intercept and slope 95% confidence intervals that were often narrower than without screening and an analysis of covariance test was passed more often. The Excel workbook WLR calculation and acceptance criteria will help laboratories implement draft method C for recreational water analysis in an efficient, cost-effective, and reliable manner. [ABSTRACT FROM AUTHOR]