Arsenic in drinking water-problems and solutions

Abstract

The current United States maximum contaminant level for arsenic in drinking water is set at 50 μg/l. Because of the cancer risks involved, Canada has already lowered the maximum contaminant level to 25 μg/l; the United States Environmental Protection Agency is reviewing the current allowable level for arsenic with a view of lowering it significantly. Various treatment methods have been adopted to remove arsenic from drinking water. These methods include 1) adsorption-coprecipitation using iron and aluminum salts, 2) adsorption on activated alumina, activated carbon, and activated bauxite, 3) reverse osmosis, 4) ion exchange and 5) oxidation followed by filtration. Because of the promise of oxidation-filtration systems, column studies were conducted at the University of Regina to examine oxidation with KMnO4 followed by filtration using manganese greensand and iron-oxide coated sand to examine the removal of arsenic from drinking water; these results were compared with the data from ion exchange studies. These studies demonstrated that As (III) could be reduced from 200 μg/l to below 25 μg/l by the manganese greensand system. In the case of manganese greensand filtration, addition of iron in the ratio of 20:1 was found necessary to achieve this removal.

Inorganic Arsenic Speciation in Groundwater Samples Using Electrothermal Atomic Spectrometry Following Selective Separation and Cloud Point Extraction

“…34 The As III is more toxic and mobile than As V . 35 Because of the variation in toxicity and removal efficiency of As III and As V , knowledge about the speciation distribution in drinking water is important. 36 The redox As species are unstable in natural waters, because of the transformation between As III and As V , due to the organic matrices, redox potential (Eh) and pH.…”

Treatment of groundwater containing Mn(II), Fe(II), As(III) and Sb(III) by bioaugmented quartz-sand filters

“…Hence, improvement of the current treatment practices, rather than additional processing steps, would be an optimal way in which to treat As-and Sb-contaminated groundwater. Sand filtration is widely used in drinking water treatment, and greensand filters (Viraraghavan et al, 1999) and household-scale sand filters (Berg et al, 2006;Voegelin et al, 2014) have been shown to remove Fe, Mn, and As simultaneously. However its biological roles in pollutant removal still remain largely unknown.…”

Sorption of Arsenic from Desalination Concentrate onto Drinking Water Treatment Solids: Operating Conditions and Kinetics

“…Arsenic cannot be easily degraded in solutions, but can be separated from water or transformed into insoluble forms by a variety of physicochemical processes, such as coagulation [7,8], membrane separation [9,10], ion exchange [11], liquid-liquid extraction [12], and sorption [13]. Selection of…”