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Quantitative real-time PCR (qPCR) assays that target the human-associated HF183 bacterial cluster within members of the genus Bacteroides are among the most widely used methods for the characterization of human fecal pollution in ambient surface waters. In this study, we show that a current TaqMan HF183 qPCR assay (HF183/BFDrev) routinely forms nonspecific amplification products and introduce a modified TaqMan assay (HF183/BacR287) that alleviates this problem. The performance of each qPCR assay was compared in head-to-head experiments investigating limits of detection, analytical precision, predicted hybridization to 16S rRNA gene sequences from a reference database, and relative marker concentrations in fecal and sewage samples. The performance of the modified HF183/BacR287 assay is equal to or improves upon that of the original HF183/BFDrev assay. In addition, a qPCR chemistry designed to combat amplification inhibition and a multiplexed internal amplification control are included. In light of the expanding use of PCR-based methods that rely on the detection of extremely low concentrations of DNA template, such as qPCR and digital PCR, the new TaqMan HF183/BacR287 assay should provide more accurate estimations of human-derived fecal contaminants in ambient surface waters.

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. CE Database keywords: Water supply; Costs; Water distribution; Rehabilitation; Regression models; Pipes.

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. DOI: 10.1061/(ASCE)0733-9496(2002)128:4(303) CE Database keywords: Water distribution; Costs; Pipes; Rehabilitation; Excavation; Trenching; Replacement.

A major objective of drinking water treatment is to provide water that is both microbiologically and chemically safe for human consumption. Drinking water chlorination, therefore, poses a dilemma. Chemical disinfection reduces the risk of infectious disease, but the interaction between chemical disinfectants and precursor materials in source water may result in potentially harmful by-products. Chlorine consumption results in the formation of by-products, and the loss of chlorine residual reduces protection against potentially pathogenic bacteria. Therefore, much effort has been invested in characterizing the loss of chlorine residuals in raw and treated water. This paper presents a mathematical model based on the use of two second-order terms for predicting this loss or decay. DOI: 10.1061/(ASCE)0733-9496(2002)128:2(152) CE Database keywords: Pottable water; Chlorine; Mathematical models; Prediction.

Chlorination is the most widely practiced form of disinfection in the United States. It is highly effective against most microbiological contaminants. However, there is concern that the disinfection by-products (DBPs) formed by the use of chlorine might be carcinogenic. One class of DBPs that are formed and the only class of DBPs that currently are regulated are total trihalomethanes (TTHMs). Therefore, much effort is being expended in developing models that can be used to predict both TTHMs and chlorine residual levels in treated drinking water. This paper presents a model that predicts both TTHMs and chlorine residuals based on the consumption of chlorine and can be used to assist in evaluating the complex balance between microbial and DBP risks associated with disinfecting drinking water with chlorine. The parameters of the model have been found to be functions of total organic carbon, pH, temperature, and initial chlorine residual level. Bromide and the subsequent formation of brominated by-products were not considered in this paper.

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. [...]

Abstract 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.

A performance evaluation of seven end-point PCR and real-time quantitative PCR (qPCR) assays which are associated with either ruminant or bovine feces are reported. The large discrepancies in the performance of bovine-associated assays across different bovine populations and variability in assay performance between host populations indicated that the use of bovine microbial source-tracking applications would need a prior characterization at each water-shed of interest.

The quantitative PCR arrays are developed for the quantification of two human-specific genetic markers targeting Bacteriodales-like cell surface-associated genes. Assay performance combined with the prevalence of DNA targets in sewage samples have provided evidence that has supported the application of these quantitative methods for monitoring fecal pollution in ambient environmental waters.

Quantitative PCR assays are developed for the detection of bovine feces-specific genetic markers and a method is designed for the enumeration of these markers by using a Markov chain Monte Carlo approach. Acceptable assay performance combined with the prevalence of DNA targets across different cattle populations have shown that these quantitative assays are useful in monitoring bovine fecal pollution in ambient waters.

Although disinfection was one of the major public health advances in the last century and continues to be so in the twenty-first century, the disinfectants themselves may react with naturally occurring materials in treated water to form unintended by-products, which may themselves pose risks. This is of particular concern with regard to the use of chlorine. Generation of disinfection by-products (DBPs) has been shown to be a function of various factors including total organic carbon concentration, type of organic precursor, chlorination level, pH, temperature, reaction time, and UV-254 absorbance. Another factor affecting DBP formation is the presence and concentration of the bromide ion in the raw or finished water. Bromine substitutes for chlorine to produce bromine-containing homologues of the more familiar chlorine species. The current list of by-products targeted for regulation contains brominated and mixed bromine-chlorine species of total trihalomethanes and haloacetic acids. These are known to form in bromide-containing waters when chlorinated. To control chlorination DBPs therefore requires an understanding of the factors that influence their formation. This paper presents a model that can be used to predict the formation of chlorinated, brominated, and mixed species compounds based on initial chlorine concentration, chlorine consumption, bromide ion concentration, and pH. The model clearly shows that higher levels of bromide in the water favor the formation of brominated compounds. Brominated compounds also form faster than chlorinated compounds.