Removal of As(III) from water by oxidation/coprecipitation-adsorption on Fe/Al hydroxide - Process demonstration

Arsenic contamination in groundwater is a major health problem for populations who utilise that water for drinking. Arsenic(III) is often the main oxidation state that occurs in water and its pre-treatment by oxidation to arsenic(V) is considered to lead to more effective removal in subsequent coprecipitation processes. Hypochlorite is an effective oxidant for As(III). The change in solution redox potential (EH) when OCl- is added to As(III) can be used as a means for monitoring additions of the oxidant. Undesirable excessive addition of OCl- to water under treatment could be minimised through E H monitoring. The slow kinetics of the oxidative reaction by OCl- can be catalysed by Br ions in solution. A bench scale process unit has been developed for demonstrating the arsenic removal process in which oxidation and the use of a mixed Al(III)/Fe(III) coagulant is applied