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

The presence of arsenic in groundwater is a global problem, with many different technologies employed to pro -duce 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 & REG; E 33 to treat groundwater used for drinking water supply in Vi s nji cevo (Republic of Serbia). This water presents the following treatment challenges: a) more than 80% of the 126 & PLUSMN; 8.97 & mu;g/L arsenic present is arsenite (As(III)), and is therefore neutral at the high pH (8.05 & PLUSMN; 0.15) of the water and b) there is 1.33 & PLUSMN; 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 & PLUSMN; 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 & REG; E 33 is a technologically viable treatment ap-proach for small water systems.