Download or read book Understanding N nitrosodimethylamine Formation in Water written by Huong Thu Pham and published by . This book was released on 2017 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of N-nitrosodimethylamine (NDMA) in drinking water systems is a concern because of its potential carcinogenicity and occurrence at toxicologically relevant levels. The postulated mechanism for NDMA formation involves a substitution between dichloramine and amine-based precursors to form an unsymmetrical dimethylhydrazine (UDMH), which is then oxidized by ground-state molecular oxygen to form NDMA. However, this latter reaction is spin forbidden, thus likely occurs at a slow rate. It is hypothesized that the reaction between monochloramine and hydroxylamine (a nitrification product) may form an intermediate, which is involved in the NDMA formation pathway. This intermediate may also be generated from dichloramine decay, in the absence of hydroxylamine. In this study, a series of batch kinetic experiments were conducted to investigate the decomposition of chloramine species at pH 8.0 to 10.0 and the concomitant formation of NDMA. Chloramine species were quantified using UV/Vis spectroscopy (Direct UV) and colorimetric methods (Hach) and compared to simulations from the unified chloramine model. NDMA was quantified using GC-MS following liquid-liquid extraction. The model captured the decay of monochloramine and dichloramine adequately, with the exception of monochloramine at pH 10.0, possibly due to an interference from a previously reported unidentified chloramine decomposition compound (UC1). NDMA formation was pH dependent with the maximum yields at pH 9.0 and the fastest kinetics at pH 10.0. A second unidentified compound (UC2), with a mass spectrum identified as UDMH, was detected only at pH 9.0 and 10.0 in batch reactors with DMA and dichloramine. Importantly, NDMA formation appeared to be insensitive to the presence or absence of UC2, suggesting UC2 was not involved in NDMA formation. Hydroxylamine accelerates the decomposition of monochloramine. The reaction between DMA and hydroxylamine formed a third unidentified compound (UC3), preliminarily identified as acetoxime, which was not observed in the presence of monochloramine. Upon addition of hydroxylamine, NDMA yields decreased by more than half in batch reactors with DMA and monochloramine. On balance, the findings suggest the existence of a NDMA formation pathway that may not involve UDMH, and points to the need for studies with scavengers and donors of short-lived species from chloramine decay.

Download or read book N nitrosodimethylamine Formation During Chlorination of Diuron with Influence Analysis of the Sacramento San Joaquin Delta Water Quality for Urban Uses written by and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Diuron is a widely used phenylurea herbicide for control of broad leaf and annual grassy weeds for both agricultural and nonagricultural uses. With the combination of the heavy usage and its persistence in typical environmental conditions due to its physical and chemical properties, diuron has been observed frequently in California's water sources. In this study diuron is of concern due to the potential formation of N-nitrosodimethylamine (NDMA), a potent carcinogen that has been identified as an emerging disinfection byproduct (DBP) in drinking water. The first results identified that diuron is a specific NDMA formation precursor that arises from non-point sources, and highlighted the difficulties associated with determining the environmental safety of chemicals and their associated potential byproducts. The influence of additional nitrogen sources on the NDMA formation mechanism during chlorination of diuron was also studied with consideration that the dominant nitrogen-containing specie may vary between surface water and groundwater. The risks posed by representative concentrations of diuron and other reagents with respect to NDMA formation during chlorine-based disinfection may be limited even in the presence of multiple nitrogen species. A broader picture exploring the current and long-term effects of water quality on public health risks from DBP formation and drinking water treatment costs was investigated by considering the Sacramento-San Joaquin Delta system, one of the most important drinking water sources in California. The present DBPs with Delta supplies are manageable within the current treatment regulations. However, the management of Delta water as a drinking water supply would become more difficult and expensive due to a possible sea level rise in the future and western island failures, with residual health risks remaining from residual and unregulated DBPs after treatment. It is likely that water drawn directly from the Delta will pose a higher risk to public health and be more difficult to treat by conventional treatment technologies, indicating that modification of existing treatment operations or addition of new technologies may be required, with higher treatment costs.

Download or read book Stability Formation Potential and Removal of N nitrosodimethylamine NDMA in Drinking Water written by Xiaoyan Qin and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Prevention of the Formation of N nitrosodimethylamine NDMA During Wastewater Chlorination written by William Armistead Mitch and published by . This book was released on 2003 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Formation of N nitrosodimethylamine NDMA from Reaction of Monochloramine with Natural Organic Matter written by Zhuo Chen and published by . This book was released on 2006 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Factors Affecting the Formation of NDMA in Water and Occurrence written by Richard Louis Valentine and published by Amer Water Works Assn. This book was released on 2005-01 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: The USEPA has classified NDMA (N-nitrosodimethylamine) as a probable human carcinogen. It is suspected that chlorination and chloramination may be contributing factors in NDMA formation. This study surveys the levels of NDMA in selected drinking water, recycled water, and wastewater, and describes how various treatment processes impact NDMA formation.

Download or read book N nitrosodimethylamine Formation in Drinking Water from the Use of Amine based Polyelectrolytes written by Keith D. Kohut and published by . This book was released on 2003 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Toxicological Profile for N nitrosodimethylamine written by and published by . This book was released on 1989 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Cation Impact on N Nitrosodimethylamine NDMA Formation from Ranitidine in Different Water Matrices written by Yiwen Lin and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Preoxidation of Two Nitrosamines Precursors and It s Effects on N nitrosodimethylamine Formation in Water written by 羅仕麟 and published by . This book was released on 2010 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Potential N Nitrosodimethylamine NDMA Formation from Water Treatment Polymers written by Piti Piyachaturawat and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: N-Nitrosodimethylamine (commonly known as NDMA) is a probable human carcinogen that has been recognized as an emerging drinking water contaminant in recent years. Previous studies have shown that certain N-containing organic compounds may form NDMA in reaction with chlorine or monochloramine and the NDMA yield is affected by the structure of the organic-N compounds, water conditions and treatment parameters. Many amine-based water treatment polymers contain organic-N functional groups and thus have been suspected as potential NDMA precursors in water treatment systems. The purpose of this research was to systematically assess the potential NDMA formation from different structural types of water treatment polymers in reactions with various oxidants and probe the possible factors that influence the NDMA formation. Robust analytical methods for detection of NDMA and the well-known NDMA precursor dimethylamine (DMA) in the reaction samples were established. The cationic polyacrylamide (cationic PAMS), aminomethylated polyacrylamide (Mannich), poly-diallyldimethylammonium chloride (polyDADMAC) and polyamine polymers were evaluated in reactions with nitrite, free chlorine, monochloramine or chlorine dioxide in aqueous solutions at circumneutral pH and room temperature conditions. This study employed high dosages of polymer and oxidant and long reaction time in order to assess the maximum potential to form NDMA. A range of operational parameters that may affect the above reactions were also evaluated.

Download or read book A Study of Riverbank Filtration and the Formation of N nitrosodimethylamine NDMA in Natural Waters written by Ashley Elisabeth Mordasky and published by . This book was released on 2005 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Formation Studies on N nitrosodimethylamine NDMA in Natural Waters written by Xianghua Luo and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: N-nitrosodimethylamine (NDMA) is a chloramines disinfection by-product and probable carcinogen to human. The California state established a 10 ng/L action level for NDMA in drinking water. Analytical method of NDMA in waters at the trace level was developed using gas chromatography/mass spectrum with chemical ionization in the mode of selected ion storage coupled with solid phase extraction. It was found that 4 utilities in Missouri using monochloramine as disinfectant had NDMA higher than 10 ng/L in drinking water. Natural organic matter (NOM), especially the hydrophilic fraction of the NOM, was found to be a predominant NDMA precursors. Basic conditions and bromide ions favor NDMA formation in natural waters. The findings reported in this dissertation provide data on NDMA occurrences in drinking water and natural waters in Missouri. The results provide valuable information about NDMA precursors in natural waters and this information could be used in the further study of mitigating NDMA formation or removing NDMA precursors in drinking water utilities. The results on factors affecting on NDMA formation provide more information for water utilities to determine operation conditions to reduce and control NDMA formation.

Download or read book A Study of the Effect of Polymers on Potential N Nitrosodimethylamine NDMA Formation at Water and Wastewater Treatment Plants written by and published by . This book was released on 2007 with total page 122 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book A Study on the Effect of Polymers on Potential N nitrosodimethylamine NDMA Formation at Water and Wastewater Treatment Plants written by and published by . This book was released on 2007 with total page 96 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Formation of N nitrosodimethylamine During Water Disinfection with Chloramine written by Stephanie Spahr and published by . This book was released on 2016 with total page 161 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mots-clés de l'autrice: water disinfection ; chloramination ; disinfection by-products ; N-nitrosodimethylamine (NDMA) ; compound-specific isotope analysis (CSIA) ; stable isotope fractionation.

Download or read book Effect of Amine based Water Treatment Polymers on the Formation of N nitrosodimethylamine ndma Disinfection By product written by Sang Hyuck Park and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In recent years, a compound N-nitrosodimethylamine (NDMA), a probable human carcinogen, has been identified as an emerging disinfection by-product (DBP) since its formation and detection were linked to chlorine-based disinfection processes in several water utilities in the U.S. and Canada. Numerous organic nitrogen compounds present in water may impact the formation of NDMA during disinfection. Amine-based water treatment polymers used as coagulants and flocculants have been suggested as potential NDMA precursors due to the presence of amine functional groups in their structures, as well as the possible presence of dimethylamine (DMA) residues in polymer products. To minimize the potential risk of NDMA associated with water treatment polymers, the mechanisms of how the polymers behave as NDMA precursors and their contribution to the overall NDMA formation under actual water treatment conditions need to be elucidated. This research involved a systematic investigation to determine whether amine-based water treatment polymers contribute to NDMA formation under drinking water and wastewater treatment conditions, to probe the involved reaction mechanisms, and to develop strategies to minimize the polymers NDMA formation potential. The investigation included five research tasks: (1) General screening of NDMA formation potential of commonly used amine-based water treatment polymers, (2) NDMA formation from amine-based water treatment polymers under relevant water treatment conditions, (3) Probing the mechanisms of NDMA formation from polyamine and PolyDADMAC, (4) Effect of water treatment processes on NDMA formation from amine-based water treatment polymers, and (5) Developing strategies to reduce polymers NDMA formation potential. Direct chloramination or chlorination of high doses of polymers in deionized water at longer than typical contact time was used in the general screening of the NDMA formation potential of water treatment polymers and in the studies to identify reaction mechanisms. On the other hand, realistic dosages of chloramines and polymers and contact time were used in simulating representative water treatment conditions to evaluate the contribution of polymers to the overall NDMA formation in real systems. On the basis of the study results, strategies were developed to reduce the NDMA formation potential of amine-based water treatment polymers, which include modification of polymer structures and treatment parameters.