Membrane Introduction Mass Spectrometry Studies of Halogenated Cyano Byproduct Formation in Drinking WaterEPA Grant Number: R828231
Title: Membrane Introduction Mass Spectrometry Studies of Halogenated Cyano Byproduct Formation in Drinking Water
Investigators: Olson, Terese M.
Institution: University of Michigan
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: August 1, 2000 through August 1, 2003 (Extended to August 31, 2004)
Project Amount: $334,666
RFA: Drinking Water (1999) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Increasing recognition is being given to the importance of non-humic precursors of disinfection by-products (DBPs) in drinking water. This is especially an issue in water supplies with low humic matter content and as more effective removal of humic matter is achieved. Proteins, peptides, and amino acids have been implicated as important precursors of halosubstituted nitriles and cyanogen halides under these conditions. Efforts to reduce the use of chlorine disinfectants have also increased the significance of brominated cyano by-products when bromide concentrations are elevated. Colorado River Water (CRW), a source of drinking water for over 20 million people, represents a water supply where these conditions collide; it is both low in humic matter and contains moderately high bromide concentrations. The proposed research seeks to: (1) determine which amino acid precursor compounds represent the most important source of these DBPs and the structural features that contribute to their reactivity; (2) characterize the kinetics and formation mechanism of chlorinated and brominated cyano-substituted DBPs; and (3) model the formation of halogenated cyano compounds in CRW.
Initial phases of the project involve a set of characterization and screening experiments that will provide the basis for selecting a subset of amino acids and peptides for later mechanistic study. The amino acid composition of CRW samples will be characterized, the relative reactivity of free and combined amino acids in CRW with chlorine and chloramine will be determined, and the formation potentials of HAN and cyanogen halides (CNX) due to the chlorination, chloramination, and bromination of model amino acids will be examined. Upon selecting a short-list of amino acid and peptide precursors, the kinetics of amino acid halogenation will be studied by applying a new on-line technique, Membrane Introduction Mass Spectrometry (MIMS). This method offers important advantages for the kinetic study of volatile by-product formation, such as cyanogen halides and nitriles, since extraction and reaction quenching steps are avoided.
Based on the proposed kinetic studies of cyano by-product formation, a model for HAN and CNX formation in CRW will be formulated. Simulation results will be compared with actual CRW chlorination and chloramination experiments. The findings of this research will help water suppliers to assess the precursor sources of HAN and CNX, gain insight into possible control strategies (e.g., controlling algal activity, adjusting solution chemistry), and assess the risk of disinfection strategies.