New Test Method for Measuring Dissolved Organic Carbon Concentration and Composition with A-TEEM Optical Spectroscopy
1. Scope
1.1 This test method covers the (1) quantification of the dissolved fraction of natural organic carbon (DOC) in the 0.1-15 mg/L range in surface and ground drinking water sources and treatment plant processing with (2) identification and quantification of the fractional DOC components (humic-like, fulvic-like and protein-like) as a function of relative aromaticity, treatability and treatment. The test method is applicable to different drinking water treatment processes including 1) conventional coagulation, sedimentation and filtration, 2) ozone followed by biologically active filtration and 3) simple filtering. Typical daily sample measurements include the Raw source water, an intermediate processing step in the treatment plant (usually after coagulation and settling) followed by the final Finished Water which is normally treated with disinfectant before distribution to consumers.
1.2 The data are analyzed using multivariate and linear methods to test DOC and its composition. The multivariate method involves PARALLEL FACTOR (PARAFAC) analysis which decomposes the fluorescence EEM data into spectral loadings and scores representing the major DOC components (Humic-like, Fulvic-like and Tryptophan-like). The common goal of the PARAFAC algorithm is to reduce multidimensionality and eliminate noise of fluorescence and background signals. The PARAFAC scores and UV absorbance at 254 nm (A254 nm) are then processed using linear regression to predict the total DOC and each component fraction in mg/L units.
1.3 Units—The values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
Keywords
Specific UV Absorbance; Total Organic Carbon; Machine Learning
Rationale
This standard is needed to facilitate quantitative and qualitative decomposition of the major components of dissolved organic carbon (DOC) because these components are important for chemical dosing during drinking water treatment and to avoid the formation of toxic disinfection byproducts (DBPs). Conventional DOC is an aggregate parameter that does not inform directly on the aromatic organic content and molecular weight distribution which determine water treatability and DBP formation potential. This optical method provides direct quantitative information on the major aromatic components in a rapid (s-min) analysis in the source water and throughout the treatment process.
The method would be implemented by water treatment laboratory operators and the information used to evaluate chemical dosing and other treatment parameters for cost savings and to help ensure regulatory compliance for DOC removal and DBPs.
The standard is needed to facilitate reliable calibration of the method and provide clear working instructions as well as clear accuracy and repeatability specifications.
