Potential N-Nitrosodimethylamine (NDMA) Formation from Water Treatment Polymers
Potential N-Nitrosodimethylamine (NDMA) Formation from Water Treatment Polymers

Author: Piti Piyachaturawat

Publisher:

Published: 2005

Total Pages:

ISBN-13:

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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.

Effect of Amine-based Water Treatment Polymers on the Formation of N-nitrosodimethylamine (ndma) Disinfection By-product
Effect of Amine-based Water Treatment Polymers on the Formation of N-nitrosodimethylamine (ndma) Disinfection By-product

Author: Sang Hyuck Park

Publisher:

Published: 2008

Total Pages:

ISBN-13:

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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.

The Llobregat
The Llobregat

Author: Sergi Sabater

Publisher: Springer

Published: 2012-06-02

Total Pages: 381

ISBN-13: 3642309399

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The Llobregat belongs to the most thoroughly studied rivers in Europe and is a paradigm of the confluence of human and natural disturbances in a single basin. Because of its location in a very densely populated region and its Mediterranean character, the Llobregat supports a mixture of irregular flow, water abstraction, excess nutrients, mining debris, and a wide array of pollutants. The aquatic organisms strive to survive in a dramatically changing river that passes through a succession of dams, weirs and channels. The long-term river monitoring as well as the research that has been carried out in the river for a long time have provided an extensive knowledge of these disturbances and their effects on the biological communities. This book highlights the available information, with emphasis on the hydrological, chemical and biological elements interspersed in the river. Experts in the field discuss the main nutrient patterns and pollutant occurrence and the responses of the biological quality elements as well as the river ecosystem to the overall natural and man-made influences.

Roles of Polydadmacs, Dithiocarbamates and Activated Carbons in Formation of N-nitrosamine Contaminants in Water
Roles of Polydadmacs, Dithiocarbamates and Activated Carbons in Formation of N-nitrosamine Contaminants in Water

Author: Lokesh Pradeep Padhye

Publisher:

Published: 2010

Total Pages:

ISBN-13:

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N-Nitrosamines are an emerging group of disinfection byproducts characterized by high carcinogenic risks at ng/L levels and by their frequent detection in water and wastewater treatment systems in the U.S. and other parts of the world. The overall goal of this research is to achieve a better understanding of the roles of common nitrosamine precursors in leading to N-nitrosamine formation in water and wastewater treatment systems. The specific objectives of this research are: (a) To probe the mechanisms of nitrosamine formation from commonly employed water treatment polymers, particularly polyDADMACs, during ozonation, (b) To evaluate the role of dithiocarbamate compounds as nitrosamine precursors in reaction with common water disinfection oxidants, and (c) To investigate the potential enhancement effect of activated carbons (AC) to promote transformation of amines to nitrosamines and identify the involved reaction mechanism. Results of this research show that, upon ozonation, polyDADMACs may yield N-nitrosodimethylamine (NDMA) at levels up to two orders of magnitude higher than current advisory guidelines for NDMA. Radical pathways may be responsible for the degradation of the quaternary ammonium ring groups in polyDADMACs to release of dimethylamine (DMA). Detection of significant amounts of nitrite after ozonation of polyDADMACs and DMA suggests the potential role of nitrosation pathway in NDMA formation. Study results also reveal dithiocarbamates as potent nitrosamine precursors with significant nitrosamine yields upon ozonation and monochloramination. Identification and quantification of reaction products suggest nitrosation and chlorinated-UDMH oxidation as primary reaction mechanisms in nitrosamine formation from ozonation and monochloramination of dithiocarbamates compounds, respectively. This research also demonstrates that many commercial AC materials may catalyze transformation of secondary amines to yield trace levels of N-nitrosamines under ambient aerobic conditions. This is a novel discovery with far-reaching implications because of the widespread usage of AC materials in numerous analytical and environmental applications. The study results show that the properties of AC materials and reaction conditions play a crucial role in the catalyzed nitrosamine formation and should be carefully selected to minimize analytical errors and undesirable nitrosamine formation in water samples. Overall, the mechanistic information obtained in this research will be useful for the water industry and research communities to develop more effective strategies to control undesirable nitrosamine formation in water and wastewater treatment systems and thus better protect the public health.

Water Reuse
Water Reuse

Author: National Research Council

Publisher: National Academies Press

Published: 2012-07-17

Total Pages: 276

ISBN-13: 0309224624

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Expanding water reuse-the use of treated wastewater for beneficial purposes including irrigation, industrial uses, and drinking water augmentation-could significantly increase the nation's total available water resources. Water Reuse presents a portfolio of treatment options available to mitigate water quality issues in reclaimed water along with new analysis suggesting that the risk of exposure to certain microbial and chemical contaminants from drinking reclaimed water does not appear to be any higher than the risk experienced in at least some current drinking water treatment systems, and may be orders of magnitude lower. This report recommends adjustments to the federal regulatory framework that could enhance public health protection for both planned and unplanned (or de facto) reuse and increase public confidence in water reuse.

Understanding N-nitrosodimethylamine Formation in Water
Understanding N-nitrosodimethylamine Formation in Water

Author: Huong Thu Pham

Publisher:

Published: 2017

Total Pages: 74

ISBN-13:

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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.