J HEALTH POPUL NUTR 2006 Sep;24(3):267-272 ISSN 1606-0997 $ 5.00+0.20 REVIEW ARTICLE © 2006 International Centre for Diarrhoeal Disease Research, Bangladesh Review of Coagulation Technology for Removal of Arsenic: Case of Chile Ana María Sancha Department of Civil Engineering, Division of Water Resources and Environment, University of Chile, Blanco Encalada 2002, Santiago, Chile ABSTRACT Coagulation technology has been used since 1970 in northern Chile for removing arsenic from drinking- water. This experience suggests that coagulation is an effective technology for the removal of arsenic. It is currently possible to reduce arsenic from 400 µg/L to 10 µg/L at a rate of 500 L/sec, assuming pH, oxidizing and coagulation agents are strictly controlled. The Chilean experience with the removal of ar- senic demonstrates that the water matrix dictates the selection of the arsenic-removal process. This paper presents a summary of the process, concepts, and operational considerations for the use of coagulation technology for removal of arsenic in Chile. Key words: Arsenic; Arsenic removal; Coagulation technology; Drinking-water; Chile INTRODUCTION The presence of hazardous concentrations of arsenic in drinking-water and the serious health effects this situa- tion is causing to untold hundreds of millions of people across the planet, have led the World Health Organiza- tion (WHO) to recommend that the maximum concen- tration of arsenic in human drinking-water not exceed 10 µg/L. Researchers in many countries are studying to identify the most feasible technologies for the removal of arsenic in their particular situations. Some removal systems recommended in the international water mar- ket involve advanced or emerging technologies which generally require extensive pre-treatment processes and/or very high construction, operation and main- tenance costs. For many affected populations, neither they nor their governments are able to afford such ex- pensive investments in infrastructure. Chile, a small but emerging nation with significant arsenic exposure through water, has faced the challenge of removal of arsenic with large-scale water-treatment Correspondence and reprint requests should be addressed to: Prof. Ana María Sancha Department of Civil Engineering University of Chile Blanco Encalada 2002 Santiago Chile Email: amsancha@ing.uchile.cl Fax: 56 2 6894171 plants since the 1970s and has developed a strategy us- ing the conventional technology which is both very ef- fective and relatively inexpensive to build, operate, and maintain. This study presents a summary of the Chilean ex- perience in removal of arsenic from water, including an overview of the problems and variables involved and a discussion of our investigations and results at the level of large-scale water-treatment facilities. BACKGROUND Chile, located along a 4,320-km strip in southwestern South America (Fig. 1), with a population of approxi- mately 15,400,000, has extensive experience in the removal of arsenic from drinking-water supplies (1,2). Due to the particular geological characteristics of Chile and its intensive mining activity, many water sources in the northernmost area and central zones of the country are contaminated with arsenic (3). In the late 1960s, it became evident that the con- sumption of water from the Toconce River—with concentrations of arsenic in the range of 600-900 µg/ L—was causing serious problems for residents of the northern zone (4). The Chilean Government commis- sioned a study by German researchers from Berkefeld Filter concerning the removal of this contaminant from drinking-water. Working together with Chilean col- leagues, these researchers ascertained the parameters required to remove arsenic from water by means of