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DEVELOP NEW TOTAL ORGANIC CARBON/SPECIFIC UV ABSORBANCE METHOD WITH EXPANDED QUALITY CONTROL
Establish optimum performance criteria for current TOC technologies for application to Stage 2 D/DBP Rule.
Develop a TOC and SUVA (incorporating DOC and UV254) method to be published in the Stage 2 D/DBP Rule that will meet requirements as stated in the Stage 1 D/DBP Rule (Revise Method 415.3, "Measurement of Total Organic Carbon, Dissolved Organic Carbon and Specific UV Absorbance at 254 nm in Source Water and Drinking Water", to include additional ruggedness data, method study data, and a combustion TOC procedure).
Investigate the cause for instrument response differences as observed between different kinds of TOC instrument systems.
Develop a method procedure that will control and/or eliminate the cause of TOC instrument response differences.
Revise Method 415.3 Quality Control section to include additional controls for the minimization and/or the elimination of instrument response differences.
Publish Method 415.3 and document in a journal article the development of the method.
The purpose of this project is to provide a total organic carbon (TOC)/specific ultraviolet absorbance (SUVA) method that will be used by the Office of Ground Water and Drinking Water (OGWDW) to support monitoring requirements of the Stage 2 Disinfectant/Disinfection By-products (D/DBP) Rule. The Stage 2 Rule requires that enhanced water treatment be used if the source water is high in aquatic organic matter prior to the application of a disinfectant. Disinfectants (chlorine, ozone, etc.) are used in the production of drinking water in order to reduce the risk of microbial disease. These disinfectants react with the organic material that is naturally present in the source water to form disinfection by-products (DBPs). Exposure to some of these by-products may pose a long term health risk. The number and nature of DBPs make it impossible to fully characterize all of the by-products formed during the treatment of drinking water and it is more cost effective to reduce formation of DBPs than to remove them from the water after they are formed. Two measurements (TOC and SUVA) are believed to be predictive of the amount of by-products that can be formed during the disinfection of drinking water and are considered to be surrogates for DBP precursors. SUVA is calculated as the ultraviolet absorption at 254nm (UV254) in cm-1 divided by the mg/L dissolved organic carbon (DOC) concentration (measured after filtration of the water through a 0.45um pore-diameter filter) and multiplied by 100. As a result, the OGWDW included a requirement in the Stage 1 Disinfectant/Disinfection By-products (D/DBP) Rule for large systems using conventional filtration treatment to remove a certain percentage of the TOC between their source water and the combined filter effluent. If the water has a SUVA concentration at or below 2 L/mg-m, then the TOC removal requirement may be waived. However, the current TOC, DOC, and UV254 methods do not include enough quality control and sample collection/preservation requirements to ensure that laboratories perform these analyses reliably. Therefore, OGWDW has requested a TOC and SUVA (incorporating DOC and UV254) method for the Stage 2 D/DBP Rule that will provide the precision and accuracy necessary to demonstrate compliance with the Stage 1 D/DBP Rule requirements. OGWDW has also requested that the precision and accuracy that can be achieved under controlled laboratory conditions for current TOC technologies be documented and evaluated. In addition, recent studies have shown that relatively large instrument response differences exist between different kinds of TOC instrument systems when analyzing the same source water matrix. These instrument response differences were noted when analyzing source waters under controlled experimental conditions. The OGWDW requested that the cause for the instrument response differences be investigated and that the cause be minimized or eliminated and documented in the new method. This important addition to the method will directly affect the quality of the monitoring data as required by Stage 1 and 2 Rule and help ensure safe drinking water.