The Removal of N‐Nitrosodimethylamine Formation Potential in Drinking Water Treatment Plants

Abstract

A long‐term (>18 months), systematic investigation was conducted to examine (1) the removal of N‐nitrosodimethylamine (NDMA) formation potential (FP) by different treatment processes under various operational conditions at nine water treatment plants in South Carolina, and (2) the occurrence of NDMA in their distributions systems. Average NDMA FP removal by alum clarification ranged from 12 to 30% during different seasons and weather conditions. Powdered activated carbon addition improved the removal of NDMA FP, especially at high doses (>4 mg/L). The use of oxidants (i.e., chlorine [Cl2] and chlorine dioxide [ClO2]), especially simultaneous application, enhanced the removal of NDMA FP and lowered the NDMA concentration in the distribution systems to <10 ng/L. However, simultaneous application of ClO2 and Cl2 led to the formation of elevated levels of chlorate. The average NDMA FP reduction by reverse osmosis and microfiltration was 81 and 7%, respectively. The overall NDMA FP removal efficiencies between raw and finished water ranged between 40 and 59%.

Two years of post-wildfire impacts on dissolved organic matter, nitrogen, and precursors of disinfection by-products in California stream waters

“…These results are consistent with studies by Wang et al ( , 2016 that showed ash sample leachates had relatively higher NDMA FP compared to their unburned source materials. Since NDMA FP did not correlate with DON or TDN (Uzun et al, 2015) and several known precursors are anthropogenic-derived (Ruecker et al, 2017;Uzun et al, 2017Uzun et al, , 2015, such an increase may be explained by the use of human-made compounds, such as fire suppressants during the fire or the release of some of the NDMA precursors by hightemperature burns. Also, carbon-normalized NDMA FP values were higher (p < 0.05) in the Rocky Fire samples (5.8 ± 2.4 ng/mg-C) compared to Wragg Fire samples (3.9 ± 1.07 ng/mg-C) during the first rainy season.…”

“…After incubation, residual oxidant was measured in all samples (oxidant content was always >10 mg/L and >20 mg/L for Cl 2 and NH 2 Cl, respectively) and quenched with a stoichiometric amount of ascorbic acid (for chlorination) or sodium thiosulfate (for chloramination) before extraction for DBP determination. Detailed descriptions for analysis of general water quality parameters, DOM characterization, analysis of DBPs, and minimum reporting levels (MRLs) are presented elsewhere (Uzun et al, 2017;Ruecker et al, 2017), and summarized in the SI. Student's t-tests were used to determine significant differences among watersheds.…”

Impact of Combined Chlorination and Chloramination Conditions on N‐Nitrosodimethylamine Formation

“…The order of efficacy was found to be as follows: O 3 > HOCl ~ medium‐pressure UV > low‐pressure UV > ClO 2 (McCurry et al , Shah et al ). Uzun et al () found that the use of chlorine and chlorine dioxide, especially simultaneous application, enhanced removal of NDMA formation potential (FP). Certain water quality parameters, such as pH, temperature, and time, can exert important effects on precursor abatement and nitrosamine formation and will vary with source water and season.…”