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Drinking water disinfection has markedly reduced diseases causes by waterborne pathogenic microorganisms. However, an unintended consequence of disinfection and/or oxidation processes is the generation of disinfection byproducts (DBPs) which are formed from the reactions of disinfectants/oxidants with water matrix components. This volume of the Comprehensive Analytical Chemistry Handbook presents recent advances about the formation, identification, and quantification of inorganic and organic DBPs during oxidative processes. The book begins with a first chapter reviewing the most recent non-targeted screening approaches and workflows to characterize DBPs using low-, high-, and ultra-high-resolution mass spectrometry. The second chapter discusses the analysis of inorganic chloramines in waters using on-site and/or in-lab analytical methods. The third chapter provides an overview of the current knowledge about the mechanisms of chlorine dioxide reactions and byproducts formation. The fourth chapter presents some fundamental and practical aspects about ozonation processes in water treatment and provides an overview about ozone reaction mechanisms and byproducts formation. The fifth chapter focuses on the reactivity of halide ions, particularly bromide and iodide, with common oxidants and the role they play in determining the speciation of DBPs in treated waters. The chapter also presents strategies to mitigate the formation of DBPs during oxidation processes. Finally, the last chapter tackles the topic of DBPs formation during potable water reuse. It discusses the formation of DBPs of major concern in both memebrane-based and non-membrane-based potable water reuse treatment schemes. Researchers, water treatment specialists, and regulators will find in this book a valuable and compact resource on several key topics regarding the formation, identification, quantification, and mitigation of DBPs. Identification and quantification of known and unknown DBPs Formation of DBPs during different disinfection/oxidation processes DBPs of concern in new technologies and/or new applications of existing technologies in water treatment
The EPA has established regulations which classify four types of disinfection byproducts - TTHMs, haloacetic acids, bromate, and chlorite - and requires public water systems limit these byproducts to specific levels. Most of the information required to comply with these standards is either scattered throughout the literature or derived from confere
Covering the latest developments in themes related to water disinfection by-products, this book brings the reader right up to date. Stemming from an international conference, contributions are from decision-makers, regulators and the relevant scientific community. Coverage includes emerging disinfection by-products, water treatment, water recycling, monitoring, regulation and health and toxicology aspects. It will be of interest to water companies, public health professionals, drinking water quality regulators, suppliers of laboratory and on-line monitoring equipment, analytical chemists, and academic and industry researchers working in the area of disinfection by-products.
In response to many U.S. water utilities that are considering changing disinfectants from chlorine to alternative disinfectants, this research has been undertaken to gain knowledge of long-term effects.
Disinfection By-Products in Water Treatment describes new government regulations related to disinfection by-products. It explains the formation of microorganism by-products during water treatment and the methods employed to control them. The book includes several chapters on chlorine by-products and discusses techniques for the removal of chloroform from drinking water. It also describes gamma radiation techniques for removing microorganic by-product precursors from natural waters and the removal of bromate from drinking water.
Assesses the impact of dynamic water quality conditions in the distribution system on the inactivation of microorganisms in bulk water. Addresses questions about the usefulness of maintaining a secondary residual and the target level to be maintained. Bridges research related to distribution system water quality with that of microbial inactivation.
The advent of drinking water disinfection to inactivate pathogens was a significant public health achievement. However, disinfectants react with dissolved organics to form disinfection byproducts (DBPs), which have been associated with bladder cancer, colorectal cancer, and adverse reproductive outcomes. After 50 years of research, it remains unclear which DBP classes drive the toxicity of disinfected drinking water. Globally, trihalomethanes (THMs) are the most commonly regulated DBP class. THMs are used as a surrogate for DBP exposure based on the assumption that they are representative of the overall DBP mixture. Two recent trends challenge this assumption: 1) the identification of hundreds of DBP species with precursors and formation pathways distinct from THMs, and 2) an increase in potable reuse of reclaimed municipal wastewater, which contains precursors that promote the formation of nitrogen-containing DBP classes (N-DBPs). Although N-DBPs are unregulated in most countries, in vitro and in vivo toxicity studies indicate they are more toxic than THMs. The four studies comprising this dissertation demonstrate that US and global DBP policy may not lead to treatment choices that effectively minimize health risk, particularly for the large population that relies on wastewater-impacted drinking water without advanced treatment. The first two studies utilized a pilot-scale system to evaluate the potential of several disinfection strategies (one existing, one novel) to minimize DBP-associated toxicity while meeting regulatory limits for pathogens and DBPs in reclaimed wastewater. The first study focused on tradeoffs between regulated and unregulated DBP formation with chlorine-chloramine disinfection. Pre-oxidation with free chlorine is effective for inactivating viruses and reducing the formation of N-Nitrosodimethylamine (NDMA), which is being considered for regulation in the US. Compared to chlorine, chloramines mitigate the formation of THMs and haloacetic acids (HAAs), which are regulated in the US. A minimal pre-chlorine contact time achieved inactivation of the virus indicator MS2 while maintaining THM and HAA concentrations below regulatory limits. A longer pre-chlorination contact time was required to reduce NDMA to target levels; however, this increased the estimated toxicity of the DBP mixture, primarily due to the formation of haloacetonitriles (HANs), an unregulated N-DBP class. The second study introduces a novel disinfection method, distributed chorine injection, to reduce NDMA formation during break-point chlorination. The efficacy of this method was demonstrated at pilot-scale, and the hypothesized mechanism was proven with kinetic modeling and bench experiments. Distributed chlorine injection is a low-cost strategy for utilities to meet low NDMA limits without increasing halogenated DBP formation. The final two studies addressed whether THMs are an effective surrogate for unregulated DBP classes. The first investigated this question in the context of treatment and infrastructure practices in low- and rising-middle income countries through a case study in Rajasthan, India. Most of the water sources were impacted by wastewater due to minimal sanitation infrastructure. The low to moderate levels of THMs measured were not indicative of high concentrations of unregulated DBPs in many drinking waters. The concentrations of toxic, unregulated DBP classes in the largest water system resembled those measured in reclaimed wastewater for nonpotable reuse. HANs were again the dominant contributor to estimated toxicity. Thus, the final study was designed to conclusively determine whether THMs are an effective surrogate for HANs. Multiple statistical models were developed using a large database of DBP concentrations measured in distribution systems of ~250 US public water systems. Multilevel/hierarchical regression models identified substantial systematic variance in the HAN:THM ratio between water systems and within distribution systems. A portion of the variance was attributed to factors such as source water type, disinfectant sequence, distribution system retention time, as well as seasonal effects on surface water. A risk ratio analysis indicated that using THMs as a surrogate for HAN exposure introduces significant classification bias. Overall, these findings underscore the need to identify the toxicity drivers in disinfected waters so that treatment systems can be designed to target those DBP classes. Furthermore, a new global policy paradigm should account for local factors influencing DBP speciation and holistically address the risk posed by complex contaminant mixtures in drinking water.