The N-nitrosomethylethylamine (NMEA), new disinfection byproducts, formation during water disinfection with chlorine

P Andrzejewski, Barbara Kasprzyk-Hordern, J Nawrocki

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

Nitrosoamines, mainly N-nitrosodimethylamine (NDMA), N-nitrosomethylethylamine (NMEA) and N-nitrosodiethylamine (NDEA) are highly mutagenic compounds that are suspected of carcinogenic activity to the human body. The US Environmental Protection Agency (US EPA) classified these compounds in the group 132 which indicates probable carcinogenicity to the human. According to the US EPA, the maximum admissible concentration of these compounds in drinking water are 7 ng L-1 (NDMA), 20 ng L-1 (NMEA) and 2 ng L-1 (NDEA) with the risk estimation of 10(-5). Up to now, knowledge of the topic of the formation of nitrosoamines has been based on the mechanism of secondary alkylamines reaction with nitrite. It was reported in 2002 that N-nitrosodimethylamine is formed during the disinfection of water and sewage with chlorine. The results indicated that chlorination of water containing dimethylamine with chlorine, in presence of ammonia ions, leads to the formation of NDMA as one of many by-products. The aim of the paper is the evaluation of the possibility of N-nitrosomethylethylamine formation as a result of methylethylamine reaction with chlorine in the presence of ammonia ions. The experiment was carried out for reaction times lasting from 0.5 up to 48 hours. After a specific time, the reaction was stopped with ascorbic acid at an equimolar ratio to sodium hypochlorite. The initial molar ratio of methylethylamine, ammonium chloride and sodium hypochlorite was 1:1:2. The optimal conditions of NMEA formation were identified as a result of an experiment carried out using different molar ratios of the substrates of reaction. As the primary aim of the research was the evaluation of the possibility of NMEA formation as a result of methylethylamine reaction with chlorine in the presence of ammonia ions, the successful result obtained after GC-LRMS analysis was fundamental to the further research. An analyte from post-reaction mixture was concentrated, according to the modified procedure proposed by Mitch et al., by means of liquid/liquid extraction with the usage of methylene chloride. The N-nitrosomethylethylamine was found in the analyzed extract of post-reaction mixture. Apart from NMEA identification, the identification of other products with the usage of mass spectra library was also undertaken. The results obtained after GC-LRMS were additionally confirmed by GC-NPD. The post-reaction solution was also analyzed directly by means of the HPLC-UV-IE technique. This method was applied for the evaluation of the influence of both the relative molar ratio of the substrates and reaction time on the concentration of NMEA formed. The results indicated that the changes in the relative ratio of the substrates influence the concentration of NMEA. An increase of concentration of ammonia ions resulted in an increase of the concentration of NMEA. However, an increase of methylamine concentration under the conditions of constant concentration of chlorine and ammonia resulted primarily in an increase of NMEA concentration up to a maximum level followed by a decrease of its concentration. The above indicates that it is not the concentration of methylethylamine and chlorine that is the essential parameter influencing the potential of NMEA formation but their relative molar ratio The obtained results revealed that NMEA is only one of many products of the reaction taking place in the aqueous solution containing methylethylamine and ammonia ions which was disinfected with chlorine. The other identified products are: ethyl(methyl)formamide and 3-ethyl(methyl)aminopropanenitrile. Therefore N-methylethylnitrosoamine can be treated as a new disinfection by-product such as THMs, HAAs, MX or NDMA.
Original languageEnglish
Title of host publicationProceedings of the 9th International Conference on Environmental Science and Technology
EditorsT D Lekkas
Place of PublicationAthens
PublisherUniversity of the Aegean
PagesA100-A106
ISBN (Print)1106-5516960-7475-33-X
Publication statusPublished - 2005

Publication series

NameProceedings of the International Conference on Environmental Science and Technology
PublisherUniversity of the Aegean

Keywords

  • nitrosodimethylamine ndma
  • N-nitrosomethylethylamine
  • NMEA
  • water treatment
  • disinfection
  • NDMA
  • chlorination
  • nitrosoamines

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