The control of N-DBP and C-DBP precursors with MIEX®

Abstract

The objective of this study was to examine the potential of Magnetic Ion Exchange (MIEX®) technology for removing nitrogenous disinfection byproduct (N-DBP) precursors while minimizing carbonaceous DBP (C-DBP) precursors in (i) surface waters, and (ii) effluent impacted waters. Samples were collected from several drinking water source waters and wastewater treatment plant effluents. The effluent impacted source waters were simulated in the laboratory by mixing treated wastewater effluents with the same source water. Formation potential (FP) tests were conducted for regulated trihalomethanes (THMs), haloacetic acids (HAAs), and selected N-DBPs (nitrosamines and halonitromethanes (HNMs)) before and after the MIEX® treatment. The MIEX® process substantially lowered UV absorbance, total organic carbon, and THM and HAA FPs in all examined water samples, ranging from 39 to 87% reduction. A relatively small portion (9–33%) of HNM precursors was removed by the MIEX® treatment. On the other hand, an increase in N-nitrosodimethylamine (NDMA) FP was observed after the MIEX® process but only for the effluent impacted waters. Soluble metals, inorganic nitrogen, and bromide in effluent impacted waters did not correlate with the increase in NDMA FP. There was no effect of MIEX® treatment on the removal of other nitrosamine species precursors. Simulations of typical water treatment and distribution systems 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 chlorine and ammonia were added simultaneously, NDMA concentration reached 36 ng/L for the water tested in the study.