The management of arsenic wastes: problems and prospects

Arsenic has found widespread use in agriculture and industry to control a v ariety of insect and fungicidal pests. Most of these uses have been discont inued, but residues from such activities, together with the ongoing generat ion of arsenic wastes from the smelting of various ores, have left a legacy of a large number of arsenic-contaminated sites. The treatment and/or remo val of arsenic is hindered by the fact that arsenic has a variety of valenc e states. Arsenic is most effectively removed or stabilized when it is pres ent in the pentavalent arsenate form. For the removal of arsenic from waste water, coagulation, normally using iron, is the preferred option. The solid ification/stabilization of arsenic is not such a clear-cut process. Factors such as the waste's interaction with the additives (e.g. iron or lime), as well as any effect on the cement matrix, all impact on the efficacy of the fixation. Currently, differentiation between available solidification/stab ilization processes is speculative, partly due to the large number of diffe ring leaching tests that have been utilized. Differences in the leaching fl uid, liquid-to-solid ratio, and agitation time and method all impact signif icantly on the arsenic leachate concentrations. This paper reviews options available for dealing with arsenic wastes, both solid and aqueous through an investigation of the methods available For the removal of arsenic from wastewater as well as possible solidification/stab ilization options for a variety of waste streams. (C) 2000 Elsevier Science B.V. All rights reserved.