Metals Removal to Low Levels Using Chemical Precipitants

摘要

For many plating plants, the proposed Metal Products and Machinery (MP&M) reductions in effluent discharge limits for heavy metals would require improvements in existing wastewater treatment programs to ensure compliance. Effective metals removal by precipitation requires rendering soluble metals insoluble followed by good solids/liquid separation of the precipitated metals from the treated water. This presentation will review and compare chemical programs for heavy metals removal. These programs include sulfide precipitation, iron precipitation, small organic metal ion precipitants such as alkyl dithiocarbamates, clay blends and polymeric metal ion precipitants. The polymeric metal ion precipitant program may offer advantages over conventional programs. The polymeric program can effectively remove and flocculate metals and is expected to meet the new MP&M limits, even in the presence of chelants or complexing agents. A reduction in sludge generation may also be realized with the polymeric program and, in many cases, chemical feed can be automated.