Base Metal and Iron Ore Mining Industry - Pollution Prevention Guidelines
Pollution Prevention Guidelines to provide technical advice and guidance to staff and consultants involved in pollution-related projects. The guidelines represent state-of-the-art thinking on how to reduce pollution missions from the production process. In many cases, the guidelines provide numerical targets for reducing pollution, as well as maximum emissions levels that are normally achievable through a combination of cleaner production and end-of-pipe treatment. The guidelines are designed to protect human health; reduce mass loadings to the environment; draw on commercially proven technologies; be cost-effective; follow current regulatory trends; and promote good industrial practices, which offer greater productivity and increased energy efficiency.
Table of Contents
- Industry Description and Practices
- Waste Characteristics
- Pollution Prevention and Control
- Target Pollution Loads
- Treatment Technologies
- Emissions Guidelines
- Monitoring and Reporting
- Key Issues
Industry Description and Practices
This document addresses the mining of ores of base metals (copper, lead, nickel, and zinc) and of iron. The documents on Aluminum and on Coal Mining and Production also deal with mining activities. The major phases in mine development are (a) exploration; (b) mine development; c) extraction (underground and open pit) and mine operation; (d) ore beneficiation; (e) storage and transport of ore; and (f) mine closure and reclamation. This document focuses on the development, operation, and closure phases.
The volume of solid waste generated, including tailings from processing, is one of the main pollution concerns in the mining industry. Removal of overburden to access the ore can pose major problems in storage and reclamation. The overburden (waste-to-ore) ratio for surface mining of metal ores generally ranges from 2:1 to 8:1, depending on local conditions. The ratio for solid wastes from underground mining is typically 0.2:1. Where concentration or other processing of the ore is done on site, the tailings generated also have to be managed. Ores with a low metal content, say, less than 0.4%, generate significant quantities of tailings.
In certain mines where ores have high sulfur content, drainage from mine workings and waste heaps can become highly acidic and can contain high concentrations of dissolved heavy metals. This acid mine drainage (AMD) can have a pH of 3 or lower; sulfate levels of 800–1,800 milligrams per liter (mg/l); copper levels up to 50 mg/l; iron levels up to 1,000 mg/l; lead levels up to 12 mg/l; zinc levels up to 1,700 mg/l; and cadmium levels of several milligrams per liter, depending on the contents of the ore. Effluent from tailings ponds may contain concentrations of chromium of several milligrams per liter. Base metal mining tailings decant may contain high concentrations of thiosalts. Chemicals used in flotation and other metal concentration processes could create toxicity problems when released in effluents.
Surface runoffs may also pose significant environmental problems through erosion and carryover of tailings and other mining residues. Explosives such as ammonium nitrate may be present in surface runoff. Transport of mined material and machinery maintenance and repair can lead to contamination of surface water. Significant levels of dust, above 3 kilograms per ton (kg/t) of ore mined, and ranging from 0.003 to 27 kg/t, may be generated by extraction activities, crushing, ore beneficiation, transport and traffic, and wind-borne losses. Significant releases of dust containing metals, including mercury, may result from the drying of the ore concentrate. Fires may result from the oxidation of sulfide-bearing materials and can present a significant hazard.