Arsenic removal - solutions for a world wide health problem using iron based adsorbents

Arsenic contamination of ground water resources used for potable water supply is an emerging problem throughout the world. Beside the use of alternative, uncontaminated water sources, water treatment for arsenic removal is often the only solution to meet the standards. The effective application of arsenic removal processes requires the knowledge of its chemistry in natural water. It is to decide whether arsenic(III) is present and to evaluate the need for an oxidation technique for arsenic(III). Different techniques exist for the removal of arsenic, which include conventional processes like ion exchange and coagulation/filtration and also emerging processes with iron oxide based adsorbents like GEH®. The latter are the most promising techniques, as they require quite low investment and are easy to operate, because they avoid dosing of additional chemicals. This article gives a short overview on arsenic removal techniques in potable water treatment and gives examples of the application of iron based adsorbents under different conditions

Entwicklung betriebssicherer Verfahren zur Arsenentfernung bei kleinen Wasserwerken Schlussbericht

Arsenic appears as arsenate-(III) but mainly as arsenate-(V) in geogene contaminated groundwaters. Beside the oxidation state of the arsenate the pH-value, the phosphate concentration as well as the volume of water which has to be treated plays an important role to choose a reliable treatment process method. To minimize arsenate-(V) coprecipitation on Fe(OH)_3, precipitation with Fe"2"+-ions or adsorption on activated alumina are useable. The loaded aluminium oxide can be regenerated by using NaOH. In special cases a nanofiltration is suitable for arsenic removal, which leads to hygenic safe solutions especially in individual supplies. The use of the granulated iron oxide in fixed-bed-adsorbers developed during the project is especially advantageous, because this material has much higher adsorptive capacity in comparison with the aluminum oxide. If arsenate-(III) appears in the water, an oxidation to arsenate-(V) is required. For oxidation of arsenate-(III) the oxidation agents Fenton's reagent (H_2O_2) and Fe(II)) and potassium permanganate were tested. Furthermore, the following methods were tested: UV-induced oxidation, catalytic oxidation with activated carbon and oxidation with solid #delta#-manganese oxid. (orig.)SIGLEAvailable from TIB Hannover: F95B1074 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekBundesministerium fuer Forschung und Technologie (BMFT), Bonn (Germany)DEGerman