Pilot study on arsenic removal from phosphate rich groundwater by in-line coagulation and adsorption

Abstract

The presence of arsenic in groundwater is a global problem, with many different technologies employed to produce safe drinking water. However, few techniques are suitable for application in small water utilities, especially in less developed countries. This paper investigates a pilot-scale treatment using in-line coagulation with FeCl3 and adsorption on commercial iron oxide, Bayoxide® E 33 to treat groundwater used for drinking water supply in Višnjićevo (Republic of Serbia). This water presents the following treatment challenges: a) more than 80% of the 126 ± 8.97 µg/L arsenic present is arsenite (As(III)), and is therefore neutral at the high pH (8.05 ± 0.15) of the water and b) there is 1.33 ± 0.05 mg/L of phosphates present, which can compete with arsenic for surface sites on the adsorbent. During the pilot-scale investigation, these drawbacks were overcome by introducing a pretreatment applying pH correction to pH 7 and oxidising the water with chlorine. This pretreatment increased the effectiveness of in-line coagulation which reduced the arsenic concentration in the groundwater by 70 ± 7%, extending the operational life of the adsorbent. These results indicate that pH correction, preoxidation, in-line coagulation and adsorption on commercial iron oxide Bayoxide® E 33 is a technologically viable treatment approach for small water systems.