Wednesday, April 2, 2008 : 2:20 p.m.

Iron Biomineralization: Implications on the Fate of Arsenic in Landfills

Fernando Javier Alday, PhD, student, Wendell P. Ela, Ph.D. and Eduardo A. Saez, Ph.D., University of Arizona

The new 10 ppb standard for arsenic in drinking water will cause a significant increase in the volume of arsenic-bearing wastes generated by drinking water utilities. Because of its high adsorption capacity and low cost, iron sorbents will be widely utilized as a treatment option and comprise the bulk of the waste generated. Based on TCLP results, these wastes will be disposed of in municipal landfills where reducing conditions predominate, because of the high natural organic matter content and correlated microbial activity. Iron and arsenic will be reduced and, as a consequence, arsenic will be released to the leachate. Shewanella putrefaciens (strain CN32) and Geobacter metallireducens (strain GS-15) are well-known organisms that grow through the reduction of ferric iron. Iron reducing bacteria convert iron (hydr)oxides into biological iron minerals. Biomineralization consists of the transformation of ferric (hydr)oxides into ferrous iron crystalline forms, such as siderite, vivianite and iron sulfide, and into  mixed valent mineral forms, such as magnetite and green rust. In the ongoing study, biomineralization is evaluated as a key component in the processes controlling iron and arsenic leaching from arsenic-bearing waste sorbents in landfills. More importantly, biomineralization is being considered as a potential engineered process by which arsenic/iron minerals might be generated with an overall goal of stabilizing arsenic in recalcitrant crystalline mineral phases. It is well known that landfill conditions can favor iron reduction and mineralization. The goal of the research reported is to develop an economically feasible means of manipulating this process so that it is robust and reproducible, and the mineralogic end products are environmentally benign.  Early work, using lactate as the sole carbon source, suggests that after a short early period of iron and arsenic leaching, the microbial activity in laboratory columns can limit subsequent leaching to below 1ppm for both arsenic and iron.

Fernando Javier Alday, PhD, student, University of Arizona PhD student in Environmental Engineering, since January 2007, University of Arizona. MS in Environmental Engineering, University of Arizona, 2006. MBA, Universidad Catolica de Cordoba, Argentina, 2003. BS in Mechanical Engineering, Universidad Catolica de Cordoba, Argentina, 1996. Experience: Research assistant, University of Arizona, since January 2005. Research focus on treating arsenic residuals generated from water treatment processes. Previous experience: Project manager and responsible of environmental issues, Renault Argentina, Automobile Company, 1997 to 2004.

Wendell P. Ela, Ph.D., University of Arizona Dr. Wendell Ela, an Associate Professor at The University of Arizona, teaches water and wastewater treatment processes. He received his Ph.D. from Stanford University. His research focuses on treatment of inorganic contaminants and field application of innovative technologies. Over 40 papers, presentations, and sponsored workshops have come out of the work of his arsenic research group, which focuses on assessment and disposal options for arsenic treatment residuals. He is currently working with the National Institute of Environmental Health, Arizona Water Sustainability Program and EPA to quantify and predict the environmental hazard posed with disposal of arsenic residuals in landfills.

Eduardo A. Saez, Ph.D., University of Arizona Dr. Saez joined the University of Arizona faculty in 1998. Prior to that he was a professor at Simon Bolivar University in Caracas, Venezuela, and, more recently, Research Professor at North Carolina State University. In 1992, he was a Marie Curie fellow at the University of Bristol, England. In 2005-2006, he was a Visiting Scientist at Pacific Northwest National Laboratories.


2008 Ground Water Summit