Many of the available arsenic treatment methods depend on the adsorption of arsenic onto oxides and oxyhydroxides of iron.  Spent oxides are normally not regenerated, but are disposed of as waste.  By creating renewable iron oxide filters in the aquifer surrounding a production well arsenic levels in the delivered water are reduced to below drinking water standards, without creation of an arsenic-laden waste stream.  Filters are renewed by in situ oxidation of ambient dissolved ferrous iron, which then forms iron oxide and oxyhydroxide coated geomedia.  Oxidation processes are both abiotic and biotically mediated.  In aquifers where ambient iron concentrations are insufficient to bring about desired levels of arsenic removal, additional iron is introduced into the aquifer and then oxidized.  In theory, these filters can be renewed and used for centuries; in practice, the technique has over 50 years of global practical application.  We present the development of this technique from the operation of a field-based proof of concept laboratory to the construction and operation current full-scale commercial installation.  Design principles are presented along with pre- and post-treatment water quality results.  Aquifer selection criteria are introduced and the positive and negative implications of certain aquifer characteristics are discussed.  Capital, operations, and maintenance cost commitments are presented.