Commonwealth of Australia 2010
Heap leach operation and management
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- 81.2Cyanide waste management
- 81.2.2Sea dumping of cyanide wastes
- 81.2.3Trans-national waste movement
- 81.2.4States and territories waste management
81.1Heap leach operation and managementWhereas there have been numerous heap leach operations in North America and elsewhere, this technique has had relatively little use in Australia (Section 5.2.2). No published guidance is available specifically on the management of heap leach operations in Australia, though a range of general guidance documents on cyanide management is available. Information for heap leach operations is available from various sources overseas. Thiel and Smith (2003) identify a range of potential environmental risk issues associated with geotechnical aspects of heap leach operations (Table 11.). Table 11.. Summary of key concerns of heap pads and heaps
81.2Cyanide waste management81.2.1International requirements for cyanide waste managementInternational requirements for the management of cyanide-containing wastes are incorporated in various Conventions to which Australia is a signatory. The Basel Convention aims to protect the environment and human health from the improper disposal of hazardous wastes (Department of Foreign Affairs and Trade, 1992). The Basel Convention has three key objectives:
Cyanide-containing wastes from heat treatment and tempering operations (Y7), inorganic cyanides (Y33) and organic cyanides (Y38) are classified as Hazardous Wastes (Annex 1) in the Basel Convention (Department of Foreign Affairs and Trade, 1992). No organisations have been authorised to export cyanide-containing wastes from Australia. Under Article 11 of the Basel Convention, Parties to the Convention may enter into bilateral, regional or multilateral agreements or arrangements with non-Parties provided these agreements or arrangements conform to the environmentally sound management of such wastes as required by the Convention. Australia is a signatory to two such multilateral agreements including:
The Basel Convention and associated Conventions are implemented in Australia through the Hazardous Waste (Regulation of Exports and Imports) Act 1989 (Cwlth), administered by DEWHA. 81.2.2Sea dumping of cyanide wastesDEWHA administers the Environment Protection (Sea Dumping) Act, (1981), which ratifies the International Protocol relevant to the Act - Protocol for the Convention on the Prevention of Marine Pollution Dumping of Wastes and Other Matter (London Convention) (Department of Foreign Affairs and Trade, 1985). The Act provides for the regulated disposal of wastes and other substances in waters off Australia and its External Territories. The International Maritime Organisation (IMO) has Secretariat responsibilities for the London Convention and Australia is a member of the IMO. Australia is a signatory to the 1982 United Nations Convention on the Law of the Sea, which includes measures to prevent, reduce and control pollution of the marine environment by dumping of wastes (Department of Foreign Affairs and Trade, 1994). More recently, Australia has implemented the 1996 Protocol to the Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, 1972. The 1996 Protocol to the London Convention severely restricts the list of substances that may be disposed of at sea. Australia is a signatory to the Protocol for the Prevention of Pollution of the South Pacific Region by Dumping (Department of Foreign Affairs and Trade, 1986), which provides that all appropriate measures are taken to prevent, reduce and control pollution in the Protocol Area by dumping of wastes at sea. Examples of state legislation pertaining to sea dumping of wastes include the Environment Protection (Sea Dumping) Act, 1984 (SA), the Marine Pollution Act, 1987 (NSW), the Marine (Sea Dumping) Regulations, 1982 (WA), and the Transport Operations (Marine Pollution) Regulations, 1995 (Qld). DEH/DoD (2003) provide a historical account of 39 recorded events involving the disposal of cyanide salts or cyanide-containing wastes in Australian oceanic waters occurring between 1979 and 1953. Waste types disposed at sea were described variously as sodium cyanide, cyanide residues, alkaline cyanide solution, neutralised electroplating vat waste, carbonate/cyanide, pots, cyanogen bromide, cyana-gas or heat treatment salts. Records indicate ~80 000 L was disposed of at sea, plus three disposal events involving a total of ~26 tonnes of cyanide wastes (typically in drums) and 19 cyanide-impregnated vats. Wastes were disposed of offshore from New South Wales, South Australia, Queensland, Victoria and Tasmania. BRS (2002) also describe cyanide waste disposal in the 1970’s into south east Australian marine waters (1500 m depth). There have been no reported instances of sea dumping of cyanide-containing wastes in Australian waters since 1979 and since the inception of the Environment Protection (Sea Dumping) Act, (1981), which strictly prohibits the disposal of chemical wastes at sea.
Cyanide wastes are controlled wastes under the NEPC (1998) NEPM. The NEPM provides a comprehensive, national system for monitoring and reporting all interstate movements of controlled waste. The system ensures that the controlled waste reaches the approved facilities for treatment, recycling, storage and/or disposal and thereby aims to minimise impacts to the environment and human health. Under the system, the waste producer is required to apply for a consignment authorisation number through the state or territory environment protection agency of the wastes destination. The producer is issued with a unique authorisation number for the type of controlled waste, their nominated licensed transporter and their nominated licensed waste facility. A record is kept of each shipment of controlled waste by using a 5 docket Waste Transport Certificate available from the producer's state or territory environment protection agency. The waste producer, waste transporter, operator of the disposal facility and governments of the generating, receiving and any transit states or territories are informed about each shipment. The information gathered assists in dealing with emergency situations and in gaining a better overall understanding of the movement of controlled wastes between states and territories.
The three major sodium cyanide manufacturing facilities in Australia produce gaseous, liquid and solid wastes containing the cyanide compounds. Product is recovered where practical within the processes and re-used and/or treated by various means to constituent by-products. Wastewater discharges and air emissions are monitored and environmental emissions typically only occur under license (e.g. trade waste agreements, permits) authorised by various state and territory environment protection agencies. The manufacturing facilities typically collect/recycle packaging materials, such as bulk bags, supplied to customers. Mining wastes containing cyanide include tailings, which are emitted to land in TSFs. There, reactions occur leading to the volatilisation of much of the cyanide to the atmosphere, or other attenuation processes (e.g. complexation, biodegradation; refer Section 23.3). Cyanide destruction processes are implemented prior to the point of discharge at some mines. Recycling of cyanide solutions also occurs in order to minimise chemical costs and conserve water, which is typically associated with cyanide wastes. Containers used to store and transport sodium cyanide are generally returned to the manufacturer, and some packaging materials are disposed of in TSFs. Table 11.. Primary state and territory waste management legislation and guidance
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