Lead in brass and bronze waste sand streams.

Lead in Brass and Bronze Waste Sand Streams

The clocks in most states and at the federal level are ticking down rapidly toward May 8, 1990, the effective date for Environmental Protection Agency statutes effecting safe waste disposal in both public and private landfills. This date will have a costly impact, particularly for foundries that dump spent sands contaminated with toxic metals, and rules violators will then face stiff penalties.

Over the last five years, the solid waste disposal subcommittee of the Brass and Bronze Division of the American Foundrymen's Society has supported research to reduce or eliminate toxic metals contamination in sands and bag-house dust from nonferrous foundry operations to research ways to render dangerous contaminants harmless.

The project, an outgrowth of EPA concerns about dumping potentially dangerous foundry waste materials in public landfills and monofill sites, dealt with the particular concern of wastes containing lead, a known health hazard, that could leach into underground water sources.

Though offering no specific remedy, the study arrived at several effective alternative foundry approaches toward solving the lead leaching problem. Briefly, they include:

* disposal of foundry sands as a toxic waste material...costly because of high disposal and transportation charges and the inexorable loss of toxic waste disposal sites;

* prevention of lead from entering the waste stream...use of low lead alloys whenever possible, proper control of variables influencing metal/sand penetration and setting up reactions to form lead compounds that minimize leachable lead in waste material;

* segregate foundry and municipal wastes...use monofill sites after establishing acceptable criteria for waste product disposal; monitor water wells for metallic leaching;

* treatment of lead-bearing waste material...a) remove contaminants via mechanical or aqueous scrubbing, concentrating the lead bearing components for recycling or further toxicity treatment; b) thermal/mechanical treatment...transform lead into a more stable compound, i.e., lead-silicate glass, to minimize leaching; c) metallic iron additions...in theory, iron added to waste sands diminishes the leaching process, the more chemically active metallic iron actually displacing the lead, rendering the sand nonhazardous.