AWWA WQTC53003

Arsenic (As) is a metalloid that is naturally present in drinkingwater in a variety of forms (organic and inorganic), oxidation states, and valences. Inorganic arsenic predominates in drinking water and is present as arsenate (As(V)) and arsenite (As(III)). Under typical pH conditions (6.3-9.3), As(V) exists asa divalent anion while As(III) is fully protonated and exists as an uncharged molecule. Oxidation of As(III) to As(V) may be performed in the liquid phase via the addition of chemical oxidants such as chlorine to a solution containing As(III) or by exposing the As(III)-containing solution to ultraviolet light. Alternatively, a solid-phase oxidant may be used. The specific objectives of this study were to: study the effectiveness of chlorine, permanganate, ozone, chlorine dioxide, monochloramine, solid-phase oxidizing media, and ultraviolet radiation at 254 nm, for the oxidation of As(III) to As(V); determine the effect of pH, in the range 6.3-8.3, on the oxidation of As(III) to As(V); and, determine the effect of interfering reductants such as dissolved iron, dissolved manganese, sulfide, and total organic carbon, and the effect of lowtemperature (5 degrees C) on the oxidation process. Includes tables, figures.



Keywords: Oxidation;Arsenic;Drinking Water;Oxidants;pH;Chlorine;Temperature;Ozone;Iron;Permanganate;Chlorine Dioxide;Manganese;Sulfides;Organic Carbon;Ultraviolet Radiation;Kinetics;Chloramines