| The properties of iron particles and colloids are important in understanding the properties of iron corrosion scale and deposits, iron release mechanisms, the stability and mobility of iron particles in water, and the color and turbidity of aqueous iron suspensions. Their properties are also important in source water iron removal effectiveness, particle deposition rates, and the transport of adsorbed contaminants such as organic matter, e.g., organics, heavy metals, and microorganisms, through aqueous systems. Numerous research reports have been published on iron in the areas of iron chemistry, corrosion, mineralogy, and limnology. Despite an overwhelming abundance of available information, iron control and water discoloration in drinking water systems remain poorly understood. In addition, very little practical information on iron removal processes and the removal of contaminants such as arsenic during iron removal that considers the role of iron particle properties is available. The objective of this research was to study the properties of iron colloidal particles and aggregates synthesized from the oxidation of Fe(II) by oxygen and the properties of the resulting aqueous iron suspensions. Particle properties including size, morphology, mineralogy, adsorptive characteristics, and electrostatic charge were examined. Suspension color (apparent and true), turbidity, and particle stability were monitored. The impact of water quality including pH, dissolved inorganic carbon (DIC), silicate, orthophosphate, and several polyphosphate formulations on particle and suspension properties and water quality was evaluated. Finally the adsorptive properties of iron particles formed under different conditions toward phosphate and arsenic were considered. The experimental findings of this study will improve our understanding of iron release from distribution system materials, improve source water iron treatment processes, provide a scientific-basis for using "sequesterants" and corrosion inhibitors, improve the ability to reduce red water discoloration, and improve our ability to remove iron and arsenic from source waters. |
