AWWA WQTC63958

Many nitrosamines, especially N-nitrosodimethylamine (NDMA), are potent carcinogens. Onlyrecently, NDMA was identified as a new byproduct from disinfection with chloramines. This research was performed to develop strategies and methods to minimize the formationof nitrosamines during chloramination of drinking water. Thereby, emphasis was not only puton the formation of the most prominent N-nitrosodimethylamine (NDMA), but also on other relevantnitrosamines including N-nitrosoethylmethylamine (NEMA), N-nitrosodiethylamine (NDEA), N-nitrosodi-n-propylamine (NDPA), N-nitrosodi-n-butylamine (NDBA), N-nitrosopiperidine (NPIP), Nnitrosopyrrolidine,N-nitrosomorpholine, and N-nitroso-dicyclohexylamine (NDcHxA). The nitrosamineformation potential (NFP) of selected natural waters of different origin was determined inlaboratory-based NFP-tests using preformed monochloramine. In parallel to these NFP tests, thewaters under investigation were characterized by analysis of important physico-chemical parameterssuch as pH, alkalinity, TOC, ammonium, nitrite, nitrate, boron and secondary amines. In each water,NDMA turned out to be the major nitrosamine byproduct formed during chloramination. Othernitrosamines formed were NDEA, NPYR, and NMOR; however, levels were at least one order ofmagnitude lower than those of NDMA. Only a small fraction of the formed amounts of NDMA,NDEA, NPYR and NMOR could be attributed to the corresponding secondary amine precursorsdimethylamine (DMA), diethylamine (DEA), pyrrolidine (PYR), and morpholine (MOR), indicatingthat the major portion of nitrosamine formation is related to tertiary amines. Some tertiary dimethylamines(e.g., ranitidine) were found to show conversion rates into NDMA up to 83-fold higher thanDMA. For surface waters, a good correlation was found for NDMA formation and the boron contentin the water, supposing a major impact of anthropogenic pollution on the NFP. None of the otherparameters analyzed in the basic set of physico-chemical parameters showed any similar correlation.The comprehensive evaluation of the data implies that water utilities using surface water under theinfluence of wastewater are at higher risk for nitrosamine formation during chloramination than thosemaking use of non-impacted water sources. In further investigations the nitrosamine precursorremoval by different treatment steps used in waterworks was studied in laboratory experiments and atwater utilities. Treatment steps based on riverbank filtration and artificial groundwater recharge turnedout to be capable of reducing the nitrosamine precursor amount significantly. Further precursorremoval can be obtained by activated carbon treatment, chlorination and ozonation. Investigationsconcerning flocculation with iron chloride or polyaluminum chloride, however, did not show any majorremoval of nitrosamine precursor compounds via this treatment step, as did treatment via aeration orlime softening. Secondary amines were removed during aerobic riverbank filtration in the field with anaverage efficiency of 76 % for DMA, 66 % for DEA, 52 % for PYR, 80 % for MOR. Also NDMAalready present in surface water was eliminated (>90 % removal) by the riverbank filtration process. Includes 35 references, tables, figures.

Product Details

Edition:

Vol. - No.

Published:

11/01/2006

Number of Pages:

20

File Size:

1 file , 530 KB