Removal of Low Concentrated Cadmium Ions Using Fixed-bed Sulfate-Reducing Bioreactor with FS Carrier

摘要

Recovery of heavy metal ions from their low concentrated water is developed using the activity of sulfate-reducing bacteria immobilized on a fibrous slag (FS), which was employed as both bio-carrier and particle collector medium. An up-flow type bioreactor was composed of FS packed column, where sulfate-reducing bacteria (SRB) was immobilized at a lower part. In this process, sulfate ion (SO_4~(2-)) in the liquid is biologically converted to hydrogen sulfide (H_2S), which reacts with metal ionic species to produce ultrafine metal sulfide particles. 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 water contaminated with 6 mg/l of cadmium, almost complete removal was carried out throughout the operating period, approximately 30 days. Cadmium sulfide precipitates gradually accumulated on the FS bed, and finally total amount of cadmium sulfide recovered reached 27.3 mg per unit gram of FS. The experimental result indicated that the proposed bioreactor, Sulfate-Reducing Bioreactor with Fibrous Slag carrier (SRB-FS), served as an efficient heavy metal recovery column with the aid of SRB.