Water Resources Research Act Program

Details for Project ID 2008NC107B

Development of an Analytical Method for Taste and Odor Compounds and Application to NC Drinking Water Sources and Finished Waters

Institute: North Carolina
Year Established: 2008 Start Date: 2008-03-01 End Date: 2009-08-31
Total Federal Funds: $60,000 Total Non-Federal Funds: $80,780

Principal Investigators: Detlef Knappe

Project Summary: Taste-and-odor (T&O) problems in drinking water are frequently a result of metabolites excreted by algae/cyanobacteria in the water source. Methylisoborneol (MIB) and geosmin are common causes of earthy/musty odors while other algal/cyanobacterial metabolites have been associated with a wide range of taste and odor characteristics. For example, fishy and swampy odors can be caused by such compounds as 1-heptanal; cis-4-heptenal; trans, trans-2,4-heptadienal; and trans, trans-2,4-decadienal. Septic odors can be due to the presence of 2,3-benzopyrrole (indole); dimethyl disulfide; and dimethyl trisulfide. Furthermore, grassy and vegetable odors can be associated with 1-hexanal; cis-3-hexen-1-ol; cis-3-hexenyl acetate; and trans-2, cis-6-nonadienal while fruity odors have been associated with cyclocitral and linolenic acid. Many compounds causing T&O problems can be effectively removed by the addition of oxidants (e.g., potassium permanganate, chlorine, ozone) and/or activated carbon within a water treatment plant. However, other T&O compounds may be generated during treatment and distribution. For example, both brominated and chlorinated phenols can form when water is chlorinated or chloraminated for disinfection purposes, and microorganisms in the distribution system can methylate halogenated phenols to form highly odorous anisoles such as 2,4,6-tribromoanisole and 2,4,6-trichloroanisole (odor threshold concentrations for the two haloanisoles are 0.03 ng/L!). In addition, T&O compounds can leach out of some pipe materials. One objective of the proposed study is to extend a GC-MS/MS method for MIB and geosmin, which we are currently using in our laboratory, to a suite of about 20 additional compounds that are commonly associated with T&O problems in drinking water. The analytical method includes a headspace solid-phase microextraction (SPME) step to concentrate analytes and has a detection limit of 1 ng/L for MIB and geosmin. A second objective is to apply the analytical method to (1) document the identity and concentration ranges of taste-and-odor compounds in NC drinking water sources and (2) evaluate the effectiveness of full-scale treatment practices for the removal of taste-and-odor compounds in NC drinking water treatment plants. Distribution system samples will be analyzed as well to identify whether biological processes in the distribution system lead to the production of haloanisoles. Samples will be collected on a bi-weekly basis over an 8-month period at two NC municipalities. The expected results of this research will help NC drinking water treatment plants identify which algal metabolites cause taste-and-odor problems in their source water. In addition, the effectiveness of existing treatment strategies for taste-and-odor compound removal will be determined. If existing treatment strategies do not sufficiently mitigate taste-and-odor problems, a follow-up study could be conducted to identify more effective treatment alternatives.