Litter, and two co-authors, reported in 2010 that considering the toxic effects of arsenic, the World Health Organization recommends a maximum concentration of 10 mg L-1 of arsenic in drinking water. Latin American populations present severe health problems due to consumption of waters with high arsenic contents. The physicochemical properties of surface and groundwaters are different from those of other more studied regions of the planet, and the problem is still publicly unknown. Methods for arsenic removal suitable to be applied in Latin American waters are here summarized and commented.
Conventional technologies (oxidation, coagulation–coprecipitation, adsorption, reverse osmosis, use of ion exchangers) are described, but emphasis is made in emergent decentralized economical methods as the use of inexpensive natural adsorbents, solar light technologies or biological treatments, as essential to palliate the situation in poor, isolated and dispersed populations of Latin American regions.
The authors concluded that arsenic occurs in natural waters predominantly in inorganic forms, such as arsenite (As(III)) and arsenate (As(V)). The presence of arsenic in water for human consumption causes the appearance of HACRE, an endemic illness, affecting a large number of people in LA. As(V) is more effectively removed from source waters than As(III) by iron coagulants, by precipitation of natural iron, and by adsorptive media. To remove As(III), a previous oxidation to As(V) is needed. Conventional technologies (coagulation–coprecipitation, adsorption, reverse osmosis, etc.) can be applied at medium or large scale. However, for domestic or community purposes as those frequently found in rural or urban isolated population in LA, low-cost technologies using non-expensive materials, sunlight or biological methods should be developed. However, further research is needed to find additional methods and to assess the effectiveness of the proposed technologies. In each case, the validation of the method with real waters of the site before application is mandatory.
Arsenic removal from water for human consumption seems to be a very difficult task. Not a universal method exists and the election is very dependent on the composition of waters to be treated. Socioeconomic features should be carefully taken into account to select the technology. The problem of As in LA is of the same order of magnitude as in other world regions, such as SE Asia, but it is often not described in English. Although various studies have been undertaken by numerous local researchers, and proven treatment methods for the specific water conditions have been encountered, technologies have been not yet commercialized due to a lack of interest of authorities, local industries and international agencies for financial and technical cooperation.
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