You are here:
VANADIUM CHEMISTRY ESSENTIALS FOR TREATMENT STUDIES
Citation:
Schock*, M R. AND K. C. Kelty*. VANADIUM CHEMISTRY ESSENTIALS FOR TREATMENT STUDIES. Presented at American Water Works Association Inroganics Contaminants Workshop, San Diego, CA, 2/3-5/2002.
Description:
The importance of vanadium occurrence and treatment in drinking water has been elevated by its inclusion in the Contaminant Candidate List. Though it is still too early to know the nature of new regulatory requirements for vanadium, if indeed it becomes regulated, a substantial understanding of relevant aspects of the aqueous speciation, solubility, and analytical chemistry is necessary to evluate the degree of treatment difficulty that varying regulatory proposals might pose. These relationships are also important for any water systems that might encounter vanadium contamination and need to remove it. Vanadium has been reported to contaminate drinking water from natural occurrence, industrial contamination, and even from some carbon and mineral filter media used in municipal water treatment plants. Vanadium shows an interesting and disconcernting parallel with speciation, analysis and treatment of arsenic, known to be problematic for the water industry. Vanadium potentially occurs in any of three valence states (III, IV, V) across the pH and redox potential ranges encompassed by natural and treated drinking waters. It can be a cation, unchraged complex or oxyanion in potable water, and reported solids controlling solubility include vanadium oxides and various calcium, manganese, sodium, magnesium, iron, and lead vanadates. Therefore, the mobility of vanadium through treatment and distribution and the consequent ability of normal treatment process tools to remove it is a very complex function of pH, oxidant nature and concentration, surface coordination sites, and many other related background water chemical characteristics. While any regulation would likely be based on a value for total V, because the response of vanadium to different water treatment processes is dictated by its aqueous speciation and solubility, total V analyses alone are not adequate to characterize and enable understanding of vanadium behavior and water chemistry influences on treatability during those process studies. There are three main purposes to this presentation. 1) a systematic organization of the aqueous and equilibrium chemistry of V will be presented, in order to provide a basis for understanding of how V responds to different water chemistry conditions. This enables the selection of what treatment process would be worth studying and would potentially be available to water systems. 2) A critical analysis will be given of the analytical methdology available and recommendations made for necessary V speciation analysis procedures for determining treatment feasibility and process evaluation. 3) based on the most current regulatory information available, a prognosis will be fiven for the applicability of different potential treatment, possible adverse or beneficial interactions with other treatment processes in use or contemplated for upcoming regulations, and suggestions will be made for important future research focus.