This study examined the effects of pipe materials (iron, copper, lead and PVC) and orthophosphate on chloramine decay and N-nitrosodimethylamine (NDMA) formation under stagnant, laminar and turbulent conditions using modified pipe loops. As expected, chloramine decay rates generally increased with increasing flow velocity. In the presence of orthophosphate, chloramine degradation in the iron loop increased regardless of flow conditions, whereas chloramine decay rates decreased for the copper and lead loops, especially under turbulent conditions. NDMA formation in the copper loop was consistently higher than it was in the PVC control loop under laminar conditions, supporting the theory of a possible catalytic effect of copper on NDMA formation (as reported elsewhere). Iron catalysis of NDMA formation became more prominent in the presence of orthophosphate, but copper catalysis became less significant after the addition of orthophosphate. Only in the copper loop, the released metal concentrations were decreased under laminar conditions compared with turbulent flow, and they were also reduced effectively due to the addition of orthophosphate, suggesting that the catalytic effect was not primarily due to dissolved copper but likely included copper-based solids (corrosion products).
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March 2013
This article was originally published in
Journal of Water Supply: Research and Technology-Aqua
Article Contents
Research Article|
March 01 2013
Effects of pipe materials, orthophosphate, and flow conditions on chloramine decay and NDMA formation in modified pipe loops
Hong Zhang;
1Department of Civil Engineering, University of Toronto, Toronto, Ontario M5S 1A4, Canada
E-mail: [email protected]
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Susan A. Andrews
Susan A. Andrews
1Department of Civil Engineering, University of Toronto, Toronto, Ontario M5S 1A4, Canada
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Journal of Water Supply: Research and Technology-Aqua (2013) 62 (2): 107–119.
Article history
Received:
July 18 2012
Accepted:
November 13 2012
Citation
Hong Zhang, Susan A. Andrews; Effects of pipe materials, orthophosphate, and flow conditions on chloramine decay and NDMA formation in modified pipe loops. Journal of Water Supply: Research and Technology-Aqua 1 March 2013; 62 (2): 107–119. doi: https://doi.org/10.2166/aqua.2013.077
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