Chromium removal from water: a review

Chromium is present in drinking water sources (naturally occurring or anthropogenic) in many countries throughout the world. Elevated concentrations of chromium in drinking water are carcinogenic to human beings. Different treatment methods such as coagulation followed by filtration, ion exchange, adsorption and membrane filtration are employed for the removal of chromium from water in producing drinking water. However, each of these treatment methods has some limitations and it is very often difficult to meet standards while applying these methods. This paper provides an overview of sources of chromium in water, its aqueous chemistry and health effects, as well as presenting a state-of-the-art review of the methods of chromium removal from water and discussion of their suitability under given conditions. A literature review revealed that coagulation-filtration (with and without prior reduction with iron(II)) is still the most commonly used and effective method of chromium removal from water. Adsorptive filtration and ion exchange are suitable for small-scale applications. Membrane technology is effective in removing both hexavalent and trivalent species of chromium: however, fouling of the membrane should be given due consideration and the removal process should be combined with removal of other contaminants to justify the associated costs.