XII JORNADAS DE INVESTIGACIÓN Revista Investigación Científica, Vol. 4, No. 2, Nueva época. Mayo - Agosto 2008 ISSN 1870-8196 1 Efficiency of small–scale water purification units to reduce radioactive content Juan Carlos Quiroga Cifuentes Hugo López del Río J. Ignacio Dávila Rangel Fernando Mireles García Unidad Académica de Estudios Nucleares Universidad Autónoma de Zacatecas E–mail: nyc_18@hotmail.com Abstract In order to asses the efficiency of small-scale water purification units to remove radioactive elements, gross alpha and beta activities were determined on pre- and purified water samples from four treatment plants in Zacatecas and Guadalupe cities. In general, the treatment plants were more efficient to remove gross alpha activity. The percentage of removed alpha activity ranged from 27 percent to near 100 percent. Fraction of removed beta activity varied between 0% and 77%. Radioactive levels of water samples were found to be lower than maximum permissible radioactive levels. Keywords: gross activities; bulk purified water; small treatment plants. Introduction Recently, and as an alternative to the commercial bottled water, a number of small-scale water purification units (SSWP) has begun operating in Zacatecas and Guadalupe cities. In general, they provide bulk purified water at low cost to public compared to commercial brands of water. Although water quality is subjected to national sanitary regulations (DOF, 1995), sanitary surveys are focused on