Recovery of low concentrated heavy metal ions using sulfate-reducing bioreactor

摘要

Recovery of heavy metal ions from their low concentrated water is developed on the basis of the activity of sulfate-reducing bacteria using a fibrous slag (FS) as both bio-carrier and particle collector medium. An up-flow type bioreactor was composed of FS packed column, where sulfate-reducing bacteria were immobilized at a lower part. In this process, SO_4~(2-) in the solution is biologically converted to HS~-, which reacts with metal ion species to produce ultrafine metal sulfide. Subsequently, formed particles are collected onto the FS surface in the upper part of the reactor, thereby accumulating heavy metals ions as their sulfides precipitates. In the continuous treatment of 6 mg/L of Cd~(2+) contaminated water, almost complete Cd removal was carried out during approximately thirty days. A large amount of CdS precipitates was accumulated on the FS bed (recovered CdS: 30 g/kg-FS), indicating that an artificial metal sulfide deposit was obtainable from wastewater. Moreover, in the presence of six species of metals (copper, cadmium, nickel, zinc, iron and manganese), selective removal of metals following the order of the solubility of metal sulfide were made possible by controlling the biological reaction. This bioreactor can be used for a self-metal-recovery process with the activity of SRB.