AWWA WQTC57003

Combinations of water treatment processes are employed at various water treatment plants across the nation in order to provide consumers with safe, potable water. The character of the source water influences not only the type of treatment processes selected for a given plant, but also the placement of processes in the plant. The character of the natural organic matter (NOM) and seasonal changes can affect a water treatment plant's performance. Since NOM can participate in many interactions, it is very important to characterize and remove NOM in water. For example, NOM can serve as a source of food for microbes, complex with metals in the water, and react with chlorine to produce disinfection byproducts that have possible carcinogenic effects. NOM can also compete with various water contaminants for adsorption onto activated carbon. Overall, the removal of NOM can generally enhance the quality of drinking water. Although NOM is ubiquitous in the environment, and commonly found in source waters, very little is known about the molecular level structure of NOM. Therefore, it is difficult to assess the removal and transformations of NOM during water treatment, and improve existing water treatment processes for the enhanced removal of NOM. While it has been previously determined that coagulation removes the nonpolar, high molecular weight, humic fraction of NOM, the polar, hydrophilic, non-humic fraction of NOM continues to elude removal. Thus, characterizing NOM would be a useful way for water treatment facilities to monitor NOM removal and transformations, and subsequently make necessary adjustments to treatment. However, obtaining structural information about NOM can be very difficult because many of the current analytical methods (UV spectroscopy, Fourier Transform spectroscopy (FTIR), and Carbon-13 nuclear magnetic resonance (NMR) spectroscopy) do not provide specific structural information about the compounds that comprise NOM. Although, pyrolysis GC-MS does provide molecular level information about NOM, it does not characterize polar compounds very well. This is partly because pyrolysis will release oxygenated functional groups as CO or CO2 before the accompanying organic structure become volatilized through pyrolysis. This study characterized the NOM that was within water that was sampled from water treatment plants. The research team characterized the NOM at the molecular level by employing the tetramethylammonium hydroxide (TMAH)-thermochemolysis technique. This technique provides more information than pyrolysis GC-MS because it can more readily analyze the polar and oxygenated fractions of NOM. With this technique, tetramethylammonium hydroxide methylates the oxygenated compounds, thereby making them more volatile and amenable to chromatographic analysis. Carboxylic acid groups in compounds are transformed to methyl esters, while hydroxyl groups are transformed to methyl ethers. Includes 16 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2002

Number of Pages:

20

File Size:

1 file , 430 KB