ARSENIC CONTAMINATION IN GROUND WATER: MANAGEMENT OF TREATMENT RESIDUAL

Abstract

Hybrid anion exchangers dispersed with nanoparticles of hydrated metal oxides have been used in the laboratory as well as in the field for selective removal of trace contaminants present in contaminated drinking water. Hybrid anion exchangers dispersed with nanoparticles of hydrated zirconium oxide have demonstrated fluoride removal capacity from the background of other competing anions. In this study we present a novel method of synthesis of Zr-loaded hybrid anion exchanger which showed a comparatively high degree of fluoride removal capacity. In the batch adsorption experiments with a harsh background of other competing anions such as sulphate, chloride, bicarbonate and nitrate it showed very high adsorption capacity. Continuous adsorption column studies with synthetic as well as real-life wastewater proved that the hybrid adsorbent when used in a scaled-up field-level device should provide a sustainable solution to the problem of fluoride contamination in drinking water affecting millions of people in India as well as around the Globe. The hybrid adsorbent could be regenerated effectively by raising the pH using a few bed volumes of alkali solution. Therefore, the hybrid exchanger can be regenerated and recycled, an essential virtue for low-cost treatment of fluoride contaminated water in the developing countries. The hybrid material was synthesized using locally available relatively inexpensive components. Leaching of Zr neither in the spent media nor in the treated water was observed. In fact, hydrated zirconium oxide is very stable over wide pH ranges and in both oxidizing and reducing environments; hybrid Zr adsorbent is therefore an environmentally sustainable solution for the wide-scale fluoride contamination problem. The presentation shall discuss the process of synthesis and the results of batch as well as column studies with real-life as well as synthetic contaminated water.