MONITORING DISINFECTION BYPRODUCT FORMING POTENTIAL WITH SIMULTANEOUS ABSORBANCE SPECTRA AND FLUORESCENCE EXCITATION-EMISSION MAPPING: SUPPORTING STAGE 2 EPA REGULATION MONITORING COMPLIANCE

Water treatment plants in the United States will soon (by 2012 to 2013) be required to initialize enhanced monitoring for reducing disinfection by-products (DBPs) to meet the Stage 2 levels enforced by the EPA. The key to successfully meeting these requirements lies in the treatment plant’s ability to deal with often dramatic source-water variations in natural organic matter (NOM) content. Whereas the regulated levels of NOM must be determined by measuring total organic carbon (TOC) often this parameter does not provide rapid or cost-effective qualitative or quantitative assessment of the various humic, fulvic and other aromatic NOM components. However, 2 main optical techniques namely UV absorbance and fluorescence excitation-emission mapping can be used for rapid assessment with precise identification of humic and fulvic components. This study presents data from a new type of instrument which simultaneously measures the UV-VIS absorbance spectrum and EEM. The rapid absorbance-EEM is facilitated by a single system that is more than 100 time faster than conventional scanning absorbance and fluoresence optical benches. The new system can continuously collect EEMs and absorbance spectra at a rate often greater than 1 per min with the extra capacity to monitor the UV254 absorbance and fluorescence emission spectrum excited at 254 nm in 4 ms intervals (an equivalent scan rate of 5.5 million nm/min). The EEM spectral data is corrected for all instrumental response factors including concentration dependent inner-filter effects. The accumulated EEM data sets can be modeled using conventional peak identification, PARAFAC and or PCA analysis of the fractionated samples to predict the trihalomethane forming potential (THMFP). This study compares the effectiveness of THFMP predictive models based on these three techniques and explains how these can be readily employed to facilitate the Stage 2 regulation compliance for DBP monitoring.