Speciation of iron and development of iron corrosion scales in drinking water distribution systems

Abstract

The major objective of this work is to study the speciation of iron impacted by water quality including dissolved oxygen (DO), pH, alkalinity, sulfate, chloride, and monochloramine and the development of iron corrosion scales in drinking water distribution systems. Alkalinity, pH, and monochloramine had significant impacts on iron oxidation rate, and suspended iron particle, and DO, sulfate, and chloride had a slight effect on iron oxidation rate and suspended iron particle. Except at low pH, the oxygenation process of ferrous iron to ferric iron can be well described by oxidation kinetics model which also fits the monochloramine oxidation reaction. In the initial experiment stage with pipe corrosion scales having been destroyed and the iron being released seriously, the newly formed free and amorphous iron contents increased, instable iron compound dominated the iron corrosion scales and the mass fraction of the total iron in iron corrosion scales rose. With the iron release amount being relatively stable, the free and amorphous iron contents dropped, magnetite and goethite were the main components of iron corrosion scales, and the total iron in iron corrosion scales decreased.

Keywords:

• Iron
• Oxidation
• Kinetics
• Suspended iron particle
• Corrosion scale

Acknowledgments

This work was funded by Tianjin Science and Technology Project (11ZCKFSF01700) and Water Pollution Controls and Treatment Technologies Special Project of China (2012X07404002).