Conclusions

1. Evaluating the Secondary Effects of Ion Exchange Stephanie K. L. Ishii, Treavor H. Boyer Department of Environmental Engineering, University of Florida, Gainesville, Florida Background and Objectives Results: Bench-scale and Pilot Plant Data Results: Full-scale MIEX Plant Data • Ion exchange is increasingly employed for the removal of arsenic, perchlorate, nitrate, and natural organic matter (NOM). Similar to conventional anion exchange, magnetic ion exchange (MIEX) removes NOM via stoichiometric substitution with chloride. • Despite growing use, there is virtually no discussion on the secondary changes of ion exchange or on the extent to which it affects water chemistry in the context of an entire treatment process. • Examples of secondary effects: • Virginia – Coagulant change  Lead corrosion • Maine – Ion exchange for As removal  Lead corrosion • Objectives: • To evaluate the effect of MIEX treatment on corrosion • parameters • To assess how the corrosion parameters change through a • system of unit processes including MIEX treatment NOM Chloride Figure 2. CSMR as a function of MIEX dose for bench-scale experiments Figure 3. CSMR and UV254 as a function of MIEX dose for pilot plant study Chloride Magnetic Polymer • Bench- and pilot-scale experiments show that lead corrosion potential, as measured by the CSMR, • increases with increasing MIEX resin dose • Pilot-scale results show that combining MIEX • treatment and alum coagulation achieves additional • NOM removal • The CSMR for MIEX pretreated water decreases with • increasing alum dose, thus indicating a reduction in • lead corrosion potential • Pilot results emphasize the need to evaluate MIEX • treatment as part of an interrelated system Figure 8. CSMR and Larson-Skold Index for modified monthly samples taken after every treatment process NOM Anion Exchange Figure 1. MIEX treatment schematic Conclusions Magnetic Polymer • Bench- and pilot-scale data show that MIEX treatment • increase the CSMR • Full-scale data show a more complex relationship between • MIEX treatment and the CSMR; MIEX treatment does not appear to have a significant effect on the Larson-Skold Index • Regeneration results in an influx of high chloride • concentrations that have been shown to travel through the • treatment plant • Perturbations in raw water quality (well 3 vs. well 4) affect • overall treatment • Surrogate corrosion parameters should be considered when • sequencing unit processes in order to avoid compounding • effects Figure 4. CSMR and UV254 as a function of alum dose for MIEX pretreated (0.4 mL/L) pilot plant effluent Full-scale MIEX Plant Treatment Train: Cedar Key, Florida Methodology • Secondary effects defined by surrogate corrosion parameters: • Chloride-to-sulfate mass ratio (CSMR)  indicative of lead corrosion potential • Larson-Skold Index  indicative of iron corrosion potential • Bench- and pilot-scale data were analyzed to determine the effects of MIEX treatment alone on corrosion parameters • Bench-scale data were assessed to quantify the correlation between MIEX treatment and alum coagulation • Full-scale data were collected and analyzed to determine each unit process’ effect on the two corrosion parameters Future Work • Quantify the effect of MIEX treatment on surrogate • corrosion parameters with a constant raw water source • Confirm the relationship between surrogate corrosion • parameters and corrosion events with real waters • Compare the effect of chloride, sulfate, and bicarbonate on • corrosion potential using surrogate corrosion parameters • (ratios) and absolute concentrations Figure 5. Process flow diagram for full-scale MIEX treatment plant in Cedar Key, Florida Results: Full-scale MIEXPlant Data Acknowledgements Table 1. Raw water quality Thank you to the members of Dr. Boyer’s research team for introducing me to their experiments, to Neil Doty at the Cedar Key Water & Sewer District for his assistance with sample collection, and to Dr. Treavor Boyer for his insight and motivation! References Edwards, M., & Triantafyllidou, S. (2007). Chloride-to-sulfate mass ratio and lead leaching to water. Journal AWWA, 99(7), 96-109. Figure 7. CSMR after MIEX treatment and lime softening for hourly samples taken during January Figure 6. CSMR and Larson-Skold Index for preliminary monthly samples taken after every treatment process