Abstract
Interactions of chloramine with organic nitrogen compounds during purification of water for drinking may generate carcinogenic N-nitrosodime-thylamine (NDMA) as byproduct, and it has been found that cationic amine-based water treatment polymers may be one of the important precursors of NDMA. We have analyzed experimentally the influence rule of NDMA formation during chlorination and disinfection, in order to provide technical support for reducing or even avoiding the formation of NDMA. The formation characteristics of nitrosamines during the chlorination of poly-diallyldimethylammonium chloride (polyDADMAC) have been studied during our experiments. The results show that the type of chlorinating agent is crucial for the generation of NDMA; if pH = 7, NDMA has the great potential formation; the NDMA potential formation increases with temperature. The yield of NDMA will be higher as the concentration of monochloramine is 1.5 to 2.5 times of the precursor; the variation of polymer with reaction time can explain the concentration of NDMA in terminal water of pipe network is higher than that in drinking water.
Highlights
The results show that the type of chlorinating agent is crucial for the generation of NDMA; if pH = 7, NDMA has the great potential formation; the NDMA potential formation increases with temperature
The yield of NDMA will be higher as the concentration of monochloramine is 1.5 to 2.5 times of the precursor; the variation of polymer with reaction time can explain the concentration of NDMA in terminal water of pipe network is higher than that in drinking water
In order to reduce the yield of disinfection by-products (DBPs), the process of chlorination during the production of drinking water has been replaced with disinfectants such as chlorine dioxide, chloramines and ozone, but the consequent problem is that nitrogen-containing disinfection by-products (N-DBPs)
Summary
Due to the frequent detection and obvious health risk of N-Nitrosamines in drinking water, a lot of experimental researches and theoretical analyses on how to control the yield of N-Nitrosamines in drinking water have been made in recent years, and some valuable results have been obtained, such as the reaction of amine-containing compounds (N-Nitrosamines precursors) with chloramines (mainly dichloramines) in water treatment favors NDMA formation [3] [4], the precursors of N-Nitrosamines derive from effluent scouring of surface water, tertiary amines, fungicides containing secondary amine moieties, quaternary ammonium chemicals, anion exchange resins, amine-based organic coagulants, and lower & middle molecular weight Natural organic matter (NOM) [5]. In the precursor of NDMA, amine-based polymers water treatment polymers have been got considerable attention, which are commonly used as coagulants or flocculants in water and wastewater treatment systems. Mechanisms of NDMA formation from free chlorine, chloramination or ozone of several coagulants/flocculant polymes (amine-based polymers) most commonly used in potable water treatment, have been reported [6] [7] [8]. There are no reports in the literature about the specific influencing factors and the formation rules of flocculant polymer in the process of chlorination
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