The removal of natural organic matter from selected Turkish source waters using magnetic ion exchange resin (MIEX®)

The primary objective of this work was to evaluate the effectiveness of the MIEX® process in removing natural organic matter (NOM) from selected drinking water sources of the City of Istanbul. Raw water samples from five drinking water treatment plants (Elmalı, B.Çekmece, Ömerli, Ä°kitelli, and Kağıthane) serving to about 10 million people were collected and jar-tested in laboratory. The kinetics of NOM removal at various MIEX® dose and contact times, the extent of resin saturation in multiple-loading experiments, and the impacts of MIEX® pretreatment prior to coagulation on coagulant demands were investigated. After a resin dose of 5-10 ml settled resin/l and contact time of 10-20 min, dissolved organic carbon (DOC) concentrations and specific UV absorbance (SUVA254) values obtained for all waters were <1.5 mg/l and <2 l/mg DOC-m, respectively. In addition, for all waters, 17-42% nitrate and 9-24% sulfate removals were obtained at a resin dose and contact time of 10 ml settled resin/l and 10 min, respectively. UV254 absorbance reductions up to 96% were achieved. Increasing MIEX® dose generally decreased the SUVA254 values indicating that the MIEX® resin preferentially removed UV absorbing fractions of NOM. Although some degree of initial resin saturation occurred in two raw waters up to 900 bed volume (BV) loadings, such saturations were not continuous up to 2000 BV loadings. The initial saturation was not observed for the other three waters, suggesting that MIEX® resin can be loaded up to 2000 BVs or more (not tested) without any saturation. Depending on the raw water, the application of MIEX® as a pretreatment prior to coagulation reduced the coagulant (alum) demand by 0-30 mg/l compared to the coagulation only. Results from the laboratory experiments overall indicated that MIEX® resin even at relatively low dose and short contact time effectively removes NOM in all tested raw waters and reduces coagulant demands.