The On-Demand Biogenic Sulfide System can be applied for removal of metals from waste streams.  Metals are precipitated as metal sulfides after contact with hydrogen sulfide produced in a bioreactor. 

Hydrogen sulfide is an effective reagent for removing metals from aqueous waste streams - even for waste streams containing some forms of chelated metals.  Many metals such as copper, nickel, and lead are precipitated as metal sulfides that have desirable characteristics for handling and recovery.  Additionally, use of hydrogen sulfide does not add dissolved solids to the waste stream, only protons, making water reuse/recycle a possibility.

Battelle is developing a system that produces hydrogen sulfide on-demand, coupling the production of hydrogen sulfide to its consumption for metal precipitation.  This approach eliminates the need for storage of hydrogen sulfide on-site.  Instead, hydrogen sulfide is produced in a bioreactor in which the hydrogen sulfide production can be controlled to match the demand for metal precipitation.  The reactor can be shut down during off shifts or weekends and restarted without disruption of its ability to produce hydrogen sulfide.  Thus, the technology offers a potential solution to meeting low metals discharge requirements and provides the opportunity for water conservation using inexpensive, non-toxic reagents in a robust system that can meet the demands of operation in an industrial setting.

This technology can be applied for removal of metals from waste streams including those listed below.  The effluent of some treated streams may be suitable for reuse/recycle within the plant.

• wet acid rinse streams
• chelated metal waste streams
• aqueous-based etching waste streams