Date of Award
Master of Science (MS)
Environmental Engineering and Science
Freedman, David L
The objective of this study was to examine the potential of the magnetic ion exchange (MIEXÂ®) process to remove nitrogenous disinfection byproduct (N-DBP) precursors while minimizing carbonaceous DBP (C-DBP) precursors in different water matrices. In the first phase of the study, the MIEXÂ® process was tested in raw dinking waters and waters impacted effluent from wastewater treatment plant. Samples were collected from several drinking water/wastewater treatment plants in South Carolina. The effluent impacted source waters were prepared by mixing treated wastewater effluents with a drinking water. For all samples, formation potential (FP) tests were conducted for regulated trihalomethanes (THMs), haloacetic acids (HAAs), and selected N-DBPs such as nitrosamines and halonitromethanes (HNMs) under favorable conditions of formation, before and after MIEXÂ® treatment. The removal efficiencies were compared for UV absorbance, dissolved organic carbon (DOC), and DBP FP. The MIEXÂ® process substantially lowered UV254 absorbance and DOC in all examined water samples. Some removal of dissolved organic nitrogen was observed, however, its removal was generally lower than that of DOC. Significant amounts of THM and HAA precursors were removed after MIEXÂ® process, ranging from 39 to 87%. MIEXÂ® showed a very different effect on N-DBP precursors, which indicates that these two classes of DBPs do not share common precursors. A relatively small portion, 9-33% of HNM precursors was removed by the MIEXÂ® treatment. In drinking water sources, MIEXÂ® did not remove nor contribute to N-nitrosodimethylamine (NDMA) formation, whereas a substantial increase was observed in the NDMA FP after the MIEXÂ® treatment of effluent impacted waters. The increase in NDMA FP was correlated with the contributions from the wastewater effluents in water sources. Similar increases in NDMA FP were also observed for the other Type I ion exchange resins in contact with the WWTP effluent. These traditional resins have the same functional group as MIEXÂ®. No correlation was found between soluble metals or inorganic nitrogen and the enhanced NDMA FP in effluent impacted water post MIEXÂ® treatment. Meanwhile, formation of other nitrosamine species in water did not change as a result of the MIEXÂ® process. In the second phase of the study, the MIEXÂ® process was tested with an effluent impacted stream water. The studied watershed receives a significant portion of flow from a municipal wastewater treatment plant discharge. In the summer and winter of 2011, grab samples were collected from upstream before the discharge, at the discharge, and four downstream locations in the stream. Bromide ion concentration at the WWTP effluent and in the stream after the discharge was used to calculate the effluent contribution to the stream. Wastewater effluent increased DOC, anions, and DBP precursors at the discharge location in the creek; and impacted the water quality at downstream locations. The MIEXÂ® process effectively treated the effluent impacted creek water. About 42-47% DOC, 61-68% UV254 absorbance, and 50-70% THM/HAA precursors were removed after MIEXÂ® treatment. However, the MIEXÂ® process was less efficient in treating the effluent impacted waters than the upstream creek water. The effectiveness of MIEXÂ® for the control of HNM precursors ranged between 0 to 15% in both upstream and downstream locations. MIEXÂ® did not reduce NDMA FP in the effluent impacted creed water, and an increase in NDMA FP was observed after MIEXÂ® treatment. However, this increase in NDMA FP declined as the effluent impacted water travelled to downstream. For MIEXÂ® treated effluent impacted water, simulations of typical water treatment scenarios showed that NDMA concentrations remained below 10 ng/L, when chlorine alone or 40 min chlorine contact time prior to ammonia addition were employed for post-disinfection. However, when chloramine was applied, a high level of NDMA concentration of ~35 ng/L was observed. Since MIEXÂ® significantly reduces the formation of C-DBP precursors, the use of chlorine alone or some contact time with chlorine prior to ammonia addition was not problematic for THM and HAA control during these tests. However, the use of chloramine should be avoided due to risk of enhanced NDMA formation. Overall, MIEXÂ® could not remove N-DBP precursors. If post disinfection is wisely designed, MIEXÂ® could achieve simultaneous control of C-DBP and N-DBP in drinking waters. Potential water treatment options need to be further explored for control of both C-DBP and N-DBP precursors.
Gan, Xiaojie, "THE CONTROL OF NITROGENOUS AND CARBONACEOUS DISINFECTION BYPRODUCT PRECURSORS WITH MAGNETIC ION EXCHANGE" (2012). All Theses. 2191.