Predicting Water Treatment Challenges From Source Water Natural Organic Matter Characterization

• Main Author: Bergman, Lauren E.
• Format: Others
• Published: Research Showcase @ CMU 2016
• Online Access: http://repository.cmu.edu/dissertations/781; http://repository.cmu.edu/cgi/viewcontent.cgi?article=1820&context=dissertations

Natural Organic Matter (NOM), a pervasive component of natural waters, presents many challenges for water treatment systems. Its complex and heterogeneous nature makes NOM difficult to characterize and highly variable in its effect in water treatment. Two specific water treatment challenges caused by NOM and dependent on its character are disinfection by-product (DBP) formation and organic fouling in pressure-driven membranes. Many NOM characterization methods exist and have shown success in highly controlled laboratory settings; however, evaluating their effectiveness in full-scale systems to predict DBP formation and membrane fouling remains an ongoing challenge. Fluorescence NOM Excitation Emission Matrices (EEM) are hypothesized to be effective in NOM characterization because they capture the complexity and heterogeneity of the NOM in data-rich measurements that are unique to each individual sample. The objective of this work was to assess the utility of fluorescence EEM and other NOM characterization techniques for predicting DBP formation and membrane fouling in full-scale treatment systems. The review of current literature on NOM characterization and use in predicting water treatment challenges revealed patterns among NOM characterizations and water treatment outcomes – namely, high molecular weight, hydrophobic, aromatic NOM leads to increased DBP formation, while hydrophilic NOM with low aromaticity leads to increased organic fouling. Multiple reports from laboratory studies indicating the success of fluorescence measurements in characterizing DBP formation and membrane fouling suggest evaluation at full-scale treatment plants is warranted. The two field studies presented in this dissertation each address one of the major treatment challenges outlined – DBP formation and membrane fouling. The DBP formation field study incorporated source water and finished water samples from six treatment plants along the Monongahela River in southwestern Pennsylvania to create a regional watershed model. Fluorescence measurements of the source water were used successfully to classify finished water DBPs according to various targets using classification trees. The membrane fouling study incorporated samples of the raw source water and treated water at various treatment stages within a full-scale two-pass (two-stage) reverse osmosis membrane treatment plant. Fluorescence measurements were successful in distinguishing between high fouling and low fouling periods within the plant, however, they were not capable of tracking treatability of source water throughout the pre-treatment steps. The results of the two field studies indicate that fluorescence measurements have utility in NOM characterization for full-scale treatment plant operations, but more research is needed in determining which specific signals are useful in online fluorescence detection and in assessing the broader applicability of these techniques to other geographical regions with different water qualities.