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One of the concerns facing the drinking water industry is the formation of disinfection by-products (DBPs) during the disinfection stage of treatment. Organic DBPs form during the oxidation of the natural organic matter (NOM) found in natural waters by the application of a disinfectant, such as chlorine. NOM is composed of two aggregate materials, humic and non-humic substances. It is unknown which portions of NOM react with the oxidant to form DBPs. Methods used to predict the formation of DBPs include total organic carbon (TOC) analysis and Trihalomethane Formation Potential (THMFP), which are time consuming and do not give specific information. This research explored the use of fluorescence spectroscopy to identify the humic portion of NOM and to predict the formation of DBPs.
Natural Organic Matter (NOM) plays a major role in the formation of undesirable organic by-products following disinfection/oxidation of drinking water. It is suspected that most precursors to disinfection by-products (DBPs) are humic although non-humic substances have not been studied and are suspected of also contributing to DBPs. NOM reacts with many of the disinfectants used to treat drinking water, such as chlorine, chioramine, and ozone, to form a variety of DBPs. Many of these DBPs have adverse health effects in humans (i.e. carcinogenic or mutagenic effects). The primary DBPs of concern include the trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetonitrile (HANs). The Spectral Fluorescent Signatures (SFS) technique was developed for the identification of the humic acids (HA), fihlvic acids (FA) and non-humic substances by fluorescence. The SFS is the total sum of emission spectra of a sample at different excitation wavelengths, recorded as a matrix of fluorescent intensity in coordinates of excitation and emission wavelengths, in a definite spectral window. For the characterization of NOM in raw water, and determination of DBP formation reactivities, samples were prepared using river HA and FA, soil HA and FA and peat HA and FA in varying concentrations from 0.5 to 10 ppm. UV-2 54, TOC, DBP formation potential, SF5 tests were conducted on each matrix of samples.
A core text on principles, laboratory/field methodologies, and data interpretation for fluorescence applications in aquatic science, for advanced students and researchers.
Organic matter (OM) in drinking water treatment is a common impediment responsible for increased coagulant and disinfectant dosages, formation of carcinogenic disinfection-by products (DBPs), and microbial re-growth in distribution system. The inherent heterogeneity of OM implies the utilization of advanced analytical techniques for its characterisation and assessment of removal efficiency. Here, the application of simple fluorescence excitation-emission (EEM) spectroscopy to OM characterisation in drinking water treatment was presented. Monthly raw and clarified water samples were obtained for 16 UK surface water treatment works. Fluorescence EEM spectroscopy was used for the assessment of total organic carbon (TOC) removal and OM characterisation. Fluorescence peak C intensity was found to be a sensitive and reliable measure of OM content and hence an indicator of DBPs presence. Fluorescence peak C emission wavelength and peak T intensity (reflecting the degree of hydrophobicity and the microbial fraction respectively) were found to characterise the OM; the impact of both on TOC removal efficiency was apparent. OM fluorescence properties were shown to predict TOC removal, and identify spatial and temporal variations. The simplicity, sensitivity, speed of analysis and low cost, combined with potential for incorporation into on-line monitoring systems, mean that fluorescence spectroscopy offers distinct advantages over other THM precursors characterisation techniques.
Disinfection byproducts are the result of reactions between natural organic matter (NOM) and a disinfectant. The formation and speciation of DBP formation is largely dependent on the disinfectant used and the natural organic matter (NOM) concentration and composition. This study examined the use of photocatalysis with titanium dioxide for the oxidation and removal of DBP precursors (NOM) and the inhibition of DBP formation. Water sources were collected from various points in the treatment process, treated with photocatalysis, and chlorinated to analyze the implications on total trihalomethane (TTHM) and the five haloacetic acids (HAA5) formations. The three sub-objectives for this study included: the comparison of enhanced and standard coagulation to photocatalysis for the removal of DBP precursors; the analysis of photocatalysis and characterization of organic matter using size exclusion chromatography and fluorescence spectroscopy and excitation-emission matrices; and the analysis of photocatalysis before GAC filtration. There were consistencies in the trends for each objective including reduced DBP precursors, measured as dissolved organic carbon DOC concentration and UV absorbance at 254 nm. Both of these parameters decreased with increased photocatalytic treatment and could be due in part to the adsorption to as well as the oxidation of NOM on the TiO2 surface. This resulted in lower THM and HAA concentrations at medium and high photocatalytic treatment levels. However, at no UV exposure and low photocatalytic treatment levels where oxidation reactions were inherently incomplete, there was an increase in THM and HAA formation potential, in most cases being significantly greater than those found in the raw water or control samples. The size exclusion chromatography (SEC) results suggest that photocatalysis preferentially degrades the higher molecular mass fraction of NOM releasing lower molecular mass (LMM) compounds that have not been completely oxidized. The molecular weight distributions could explain the THM and HAA formation potentials that decreased at the no UV exposure samples but increased at low photocatalytic treatment levels. The use of photocatalysis before GAC adsorption appears to increase bed life of the contactors; however, higher photocatalytic treatment levels have been shown to completely mineralize NOM and would therefore not require additional GAC adsorption after photocatalysis.
There are many by-products of water disinfection that are still not fully understood and can be potentially harmful. In this volume all the current research in this area is discussed, along with an examination of the role of NOM (natural organic matter) and its relationship to DBP (disinfection by-product) formation and control in drinking water. Understanding the relationship of NOM to DBP may well lead to new techniques for analyzing and treating water and enable reasonable choices to be made for source-water protection, treatment plant process optimization, and distribution system operation to control DBP's. This volume emphasizes the characterization and reactivity of polar natural organic matter. It examines analytical methods which better characterize NOM and determines some of the polar and nonvolatile DBP forms. It presents innovative new methods, sich as capillary electrophoresis for haloacetic aceids and LC/MS for the identification of polar dinking water DBPs.
Chemical Kinetics and Process Dynamics in Aquatic Systems is devoted to chemical reactions and biogeochemical processes in aquatic systems. The book provides a thorough analysis of the principles, mathematics, and analytical tools used in chemical, microbial, and reactor kinetics. It also presents a comprehensive, up-to-date description of the kinetics of important chemical processes in aquatic environments. Aquatic photochemistry and correlation methods (e.g., LFERs and QSARs) to predict process rates are covered. Numerous examples are included, and each chapter has a detailed bibliography and problems sets. The book will be an excellent text/reference for professionals and students in such fields as aquatic chemistry, limnology, aqueous geochemistry, microbial ecology, marine science, environmental and water resources engineering, and geochemistry.
The research reported on here sought to characterize natural organic matter (NOM) in dilute solutions and to isolate it without altering its properties, so that the effect of NOM in drinking water may be considered. Several NOM isolation methods were evaluated, including evaporation, reverse osmosis, nanofiltration, and adsorption. The effects of such isolation procedures on NOM's chemical composition and reactivity were considered. Based on these studies, the report presents conclusions regarding the feasibility and adequacy of in situ and ex situ techniques. Croue is affiliated with Laboratoire de Chimie de l'Eau de l'Environment, Universite de Poiters. Annotation copyrighted by Book News, Inc., Portland, OR.
This research examined the use and advancement of fluorescence spectroscopy as an organic characterization method in drinking water treatment, providing novel insight into the performance of and fundamental mechanisms of water treatment processes. Using fluorescence spectroscopy coupled with analysis techniques including parallel factors analysis (PARAFAC) and peak shifts, biofiltration was found to have variable impact on individual fluorophores. The fluorescence method identified production of humic-like matter by the microbial communities, ultimately resulting in a unique treated organic character of the treated water. Through correlations with formation potentials of halogenated furanones, polysaccharides were identified as possible precursors. Pre-oxidation, was suggested to result in increased proportionality of carbonyl-containing functional groups and greater carbon oxidative state. A continuous fluorescence system was developed as part of this research and implemented in two studies focused on fouling mitigation of ultrafiltration (UF) membranes. A full-scale study was conducted that continuously monitored membrane feed water organic character. Utilizing the continuous fluorescence, improved prediction accuracy of membrane fouling was found using a neural network approach. A second study, conducted at bench-scale focused on understanding the role of organic surface changes and irreversible fouling potential. Low coagulant doses (
Approximately 77 percent of the freshwater used in the United States comes from surface-water sources and is subject to natural organic matter contamination according to the United States Geological Survey. This presents a distinct challenge to water treatment engineers. An essential resource to the latest breakthroughs in the characterization, treatment and removal of natural organic matter (NOM) from drinking water, Natural Organic Matter in Waters: Characterization and Treatment Methods focuses on advance filtration and treatment options, and processes for reducing disinfection byproducts. Based on the author’s years of research and field experience, this book begins with the characterization of NOM including: general parameters, isolation and concentration, fractionation, composition and structural analysis and biological testing. This is followed by removal methods such as inorganic coagulants, polyelectrolytes and composite coagulants. Electrochemical and membranes removal methods such as: electrocoagulation, electrochemical oxidation, microfiltration and ultrafiltration, nanofiltration and membrane fouling. Covers conventional as well as advanced NOM removal methods Includes characterization methods of NOM Explains removal methods such as: removal by coagulation, electrochemical, advanced oxidation, and integrated methods