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By J. H. deur Potgieter

This paper, 'A review of the biological treatment of cyanide-bearing waste water' discusses the necessity for the treatment of cyanide-bearing waste water with a view to the avoidance of environmental pollution, and the limitations of the available chemical and physical processes are referred to briefly. The sources of cyanide-bearing waste waters are mentioned. The mechanisms of production and utilization of cyanide by fungi and bacteria are discussed. The work done in connection with the biological removal and destruction of cyanide is summarized, the successes achieved are described, and the relevant processes are listed. In conclusion, some advantages of biological processes for the removal of cyanide are mentioned.

Jan 1, 1991

1. Publications of The Institute of Metals The following publications are available from The Institute of Metals, Sales and Marketing Dept, 1 Carlton House Terrace, London SWIY 5DB, England. . Intermediate temperature embrittlement processes in duplex stainless steels. 1990. £15.00. This is a special issue of Materials Science and Technology containing the full proceedings of the international workshop held in Oxford in August 1989. . Worked examples in dislocations, by M.J. Whelan. 112 pp. £16.00. This is a concise introductory text that examines aspects of the theory of dislocations. . Introduction to creep mechanisms, by B. Wilshire. 1991. 112 pp. Well-supported by diagrams and illustrations, this concise introductory textbook allows students and engineers to increase their knowledge of modern theoretical and practical approaches to creep and creep fracture. . Powder metallurgy. A series of lectures. 1991. (Looseleaf binder). Originally published in 1986 by the Fachverband Pulvermetallurgie, this course book provides an introduction to PM technology. Divided into eight thematically distinct sections, it also contains numerous illustrations and tables, as well as 150 slides. The concluding section contains an extensive reference list to the literature for readers wishing to study topics in greater detail.

Jan 1, 1991

By H. P. Knudsen

In most open pit gold mines ore waste selection is based on estimates made from blasthole samples. These estimates frequently are biased. While it is true that high grades and "outliers" can induce a bias they may not be the only reason for the persistent bias seen at many mines. This paper focuses on a source of the conditional bias. In this paper it is shown that the poor blasthole sampling can cause a conditional bias in the estimates.

Jan 1, 1991

The following are available from Metal Bulletin Books Ltd, Park House, Park Terrace, Worcester Park, Surrey KT4 7HY, England. . World aluminium-a Metal Bulletin databook. 2nd ed. 1990. £71.50 surface, £76.50 airmail. This is a compendium of information listing salient details of companies mining bauxite and producing alumina, primary aluminium, secondary ingot, master alloys, and semi-fabricated products; aluminium trading companies; and a memoranda section listing associations, brand names, and other useful information. It is a userfriendly international reference book for aluminium buyers, traders, and producers.

Jan 1, 1991

By Gordon T. Austin

The combined value of production of natural abrasives, which includes tripoli, special silica stone, garnet, staurolite, and emery, increased about 21070 in 1989. The increase in the value of staurolite and tripoli production was the result of an increase in the quantity of materials produced and an increase in the unit value. Emery decreased due to the significant decline in the volume of the material produced. Special silica stone experienced both a decrease in unit value and quantity produced. Garnet showed a small increase in quantity, but a decrease in unit value. The silicon carbide industry saw a slight decrease in the quantity produced and a 12070 increase in the value of production. The fused aluminum oxide industry showed a 5070 decline in the quantity produced, but enjoyed a 15070 increase in the value of production. Combined production for both industries decreased 4070 in quantity but increased 13070 in value compared with those of 1988.

Jan 1, 1991

By A. L. Mular, R. P. Edwards

"The operation of flotation circuits is often regarded as a combination of art and science. Expert systems offer a method by which the art may be captured and supervisory control of flotation circuits fully realized. Operating knowledge, the art, can be consistently employed to enhance regulatory control through the judicious application of an expert system. Using an expert system, a supervisory control routine was developed, and successfully implemented, in the copper flotation circuit at Brenda Mines Ltd.The expert system ran in conjunction with regulatory PI controllers on a personal computer. The expert system received assays via an on-stream analyzer and adjusted regulatory loop setpoints as required in real-time. From its commissioning in November 1989, to the end of the mine's operation in June, 1990, the ES was enthusiastically embraced by the operators and attained operating levels superior to those achievable manually.INTRODUCTIONExpert system (ES) software springs from research into artificial intelligence and is currently making significant inroads into business and industry. Proponents of ES's make many attractive claims; they are a means of capturing the knowledge of experts and they can be programmed by non-programmers. To date, most uses of this software in the process industry are in off-line applications, meaning that the applications are not tied directly to operating (on-line) environments. Moreover, in on-line environments, they are typically employed as advisors and only suggest changes. Human operators are required to close-the-loop to the process. Yet, ES's should be applicable to operating environments and, if the claims of the proponents are valid, should also be better than existing tools. As an intelligent controller an ES must use the knowledge of experienced operators, apply it directly to a process and do this without the intervention of human operators. On-line applications have been successfully employed in the closed loop control of SAG circuits (Herbst et al., 1989) and flotation circuits (Hales, 1989). Harris and Kosick (1988) detail an implementation for flotation control at the Polaris Mine."

Jan 1, 1991

By N. D. Jagger, I. M. Arbuthnot

The recovery and destruction of cyanide in gold tailings is currently a topic of great interest for both financial and environmental reasons. The environmental problem is particularly important in the U.S.A. at present with the environmental lobby waging a campaign to eliminate the problem of migratory birds dying after drinking tailings dam wate. Tough legislation with severe fines and jail sentences for company executives have been introduced in several states for exceeding cyanide limits. To reduce cyanide levels in tailings dams chemical treatment, including acidification, alkaline chlorination, the INCO sulphur dioxide oxidation process and the Degussa hydrogen peroxide process amongst others are being. used. In addition several processes are at various stages of development for the recovery of residual cyanide from gold tailings. Among these is the process developed by Cyprus Gold and pilot tested by DSIR Industrial Development. This process uses air to strip cyanide from the acidified barren pulp and will be used at Cyprus Gold Mines Golden Cross Mine on the Coromandel Peninsula in New Zealand (Fricker & OWers 1990).

Jan 1, 1991

By Chris Joyce, Peter Ryan

Investigation of the occurrence and significance of acid drainage from mine sites in Australia has received a degree of attention in recent years. For contemporary and future projects, particularly those in hi1;1her rainfall areas, the focus on prediction and resolution of acid drainage issues is. likely to increase. This paper describes the preventative and remedial measures adopted at three metalliferous mines in northern Australia at which acid drainage was identified as a key issue with respect to project environmental management and rehabilitation. The thre case studies respectively comprise an active, ·1 recently decommissioned and an abandoned operatiou which was rehabilitated in the mid '80s.

Jan 1, 1991

By Barry J. Hansen

Mining can make two major contributions to the cleanup of the environment. The first of these is the extractive technology that has become highly developed as a result of centuries of development. Of equal impor­tance are the methodology of analysis and the development of engineering solutions that are the stock in trade of the mining industry. Despite the differences between the industries, the processes for the development of a mine and the cleanup of a hazardous waste site are similar. The characteristics that impact the ability to develop a suitable process for treating an ore body or correct­ing an environmental problem are those relat­ed to the distribution of the contaminant or metal in the host material.

Jan 1, 1991

By Marshall A. Koval

The future of mining in the United States is in question. The cumulative effects of federal, state and local environmental legislation threaten its survival as the cost of compliance skyrockets. Legislation has created pol ari zat ion between government and industry followed by court action, further increasing costs and delays on permitting and remediations. Regulations often call for excessive and rigid requirements that result in unrealistic compliance goals costing tens of millions of dollars. The costs often exceed the value of the remedy. A growing concern is that proper scientific methodologies and engineering practices are being sacrificed because of political and public pressures.

Jan 1, 1991

By Robert Dunne, Paul Gelfi, Vernon Martins

The New Celebration Gold Mine is located 32 km south of the regional mining centre of Kalgoorlie. The current mill throughput is 1.7 million tonnes per annum with a gold production of around 120,000 ounces per year. The main source of ore for the mill comes from the Hampton Boulder and Pernatty pits. Over the last two years the oxide reserves from these pits have been depleted and the harder primary sulphide ores are now being processed. This change has led to a decrease in cyanide extractable gold.

Jan 1, 1991

By H. N. McLeod, B. C. Butler, S. R. Rice

Tius paper describes the key considerations for design of impoundments for gold mine tailings. Design options available for construction are presented. The key considerations for design of a safe, economic and environmentally sensitive design are discussed. The dam design must also balance these conventional considerations with the pragmatic aspects of construction and operations and the risk of system upsets. Case examples of tailings facilities in Canada and Papua New Guinea are discussed.

Jan 1, 1991

By R. Z. Pyrih

Pressure/ ,acuum lysimeters were used to instrument column tests containing several lifts of tailings slurry, and to sample pore water as the tailings lifts dried. The results of the column testwork demonstrated that air oxidation of sulfide minerals associated wilh the tailings residue neutralized the alkalinity of the tailings pore water. Neutralization of the alkaline pH volatilized cyanide which, in turn, destabilized copper-cyanide complexes and caused the precipitation of insoluble copper from solution. Analyses of pore water samples for microbial activity indicated high plate counts. The presence of viable microorganisms in the pore water implied that degradation of cyanide was enhanced by growth and activity of cyanide-consuming microorganisms in the tailings material.

Jan 1, 1991

By S. J. Chadwick

The majority of small gold plants constructed around Western Australia were designed for short lives and treatment of oxide ores. The crushing plant frequently bore the brunt of capital cost savings resulting in inadequate design and equipment selection. The exhaustion of oxides and progressionto more competent ores is _ resulting in plant operators seeing their he majority of small gold plants constructed around Western Australia were designed for short lives and treatment of The net result of many of extended operating hours, low inability to achieve fine mill blow out in operating costs, the above is throughput, feeds and a oxide ores. The crushing plant frequently bore the brunt of capital cost savings resulting in inadequate design and equipment selection. The exhaustion of oxides and progression to more competent ores is resulting in plant operators seeing their operating costs spiral upwards. Steps taken at Jubilee mine to improve plant productivity and lower mechanical failure will be discussed. operating costs spiral upwards. Steps taken at Jubilee mine to improve plant productivity and

Jan 1, 1991

By W. J. C. Meynink

In drier regions of the world, total containment of cyanide liquors for rainfalls less than a specific design value is often required by government regulation. For example, in Queensland total containment is required for rainfalls up to 'the 1% annual exceedence probability. In equatorial regions, where rainfall greatly exceeds evaporation, a total containment requirement is unrealistic and this is recognized by regulatory authorities. Regulatory constraints typically require that cyanide concentrations at an agreed downstream compliance point not exceed a specific value more than a specified fraction of the time. While the excessive rainfall prevents total containment, it does provide substantial dilution. This paper outlines a methodology for assessing the distribution of cyanide concentrations at a downstream compliance point in an equatorial region with limited hydrometeorological data. Consider the hypothetical mine environs depicted in Figure 1. The mine is located near the catchment divide and draws its water supply via a gravity line. Tailings from the process plant are piped to a tailings dam on a sub-catchment below the plant site. The objective is to determine the distributions of cyanide species concentrations at a compliance point just upstream of a major settlement to ensure they do not exceed regulatory limits.

Jan 1, 1991

By Ivan Hunter, Gary Johnson

In many comminution circuits based on SAG mills, an operating cost penalty is incurred in terms of high unit power consumption. By the addition of a crusher to the circuit, to crush part of the so­called critical size fraction extracted from the mill charge, the power efficiency of the circuit can be significantly improved. Dominion Mining has now incorporated pebble crushing into three of its comminution circuits. The improvements in circuit performance have in all cases been significant, and in some cases dramatic.

Jan 1, 1991

By W. P. Staunton, K. Jones

INTRODUCTION The increased activity in the Aus­tralian gold industry over the last decade has resulted in a concomitant increase in the use of sodium cyanide, with a projected consumption of 80,000 tonnes in 1991. Growing environmental awareness by government, industry and the public has generated increased interest in the fate of cyanide near gold mine tailings dams and has highlighted the lack of basic knowledge in the area, particularly for Australian conditions. In 1989 the Chemistry Centre (W.A,) commenced a' project, under the auspices of the Australian Mineral Industries Research Association entitled "Fate of cyanide in the Enviroment Near Mine Tailings" to investigate some of the issues arising from the management of tailings containing cyanide, The project, which has been supported by thirteen companies has three broad aims:

Jan 1, 1991

By David E. Peterson, F. Merz

The Waihi Gold Mining Company Limited, Martha Hill Project was the first major hard rock mining operation following the resurgence of the mining industry in New Zealand. Because of its location adjoining a town and at the southern part of the sensitive Coromandel Peninsula, the operation received a high level of public scrutiny. Very srrict limits for effluent criteria had to be met and led to the necessity for advanced wastewater rreatment technology. The process technology selected was the copper catalysed oxidation of cyanide using hydrogen peroxide, with subsequent removal of heavy metals by precipitation and filrration. This paper discusses the adoption of environment limits together with the detailed description of the plant and design criteria. Data of the one year's operational history is also presented.

Jan 1, 1991

By L. D. Jayaweera, R. G. Robins

The pocessing of gold bearing sulphide minerals wr ich contain arsenopyrite and other complex arsenic sulphide minerals results in arsenic containing emissions and effluents which must be given careful consideration in relation to clean air and clean water standards. The sources of arsenic and the various process options for treating arsenical gold ores and concentrates are briefly reviewed. The problem relating to the removal of arsenic from gaseous emissions from roasting processes is considered. Residues from aqueous processing contain a variety of arsenical materials which have not been characterised, and the long-term stability of these is suspect. 'rhe use of lime to stabilise aqueous residues as either calcium arsenate or calcium arsenite has been shown to be inadequate for long term disposal since both compounds are converted into calcium carbonate due to the influence of carbon dioxide in the atmosphere. Ferric ion solutions have been used to precipitate ferric arsenate or to form ferric hydroxide which binds the arsenic for short term disposal, The long term stability of these ferric materials is poor, but could lead to the acceptance of a slow release option rather than complete containment of residues.

Jan 1, 1991

By W. Hopkin

INTRODUCTION Necessary science and technology are not well established for the design of responsible treatment and disposal of arsenical residues from refractory gold ores. Specifically, there is uncertainty about the precise composition and behaviour of oxidised arsenic species in these wastes, and an analysis of possible chemical behaviour suggests that potentially difficult control and disposal problems remain to be so 1 ved. In tackling these the undoubted toxicity of arsenic in excess and its bad press should not blind one to the realities of actual behaviour in the environment, and that some adverse behaviour inevitably has to be to 1 erated as a cost in return for the recovery of an operation's gold for society. The problem is to minimise any such cost. Each refractory ore will be different. Many will contain so little arsenic that it will cause only trivial problems in disposal, but there remain others with significant arsenic content, say in the order of 1% or more, to cause concern. As already implied, concern can be over emphasised but equally underestimated. The balance which must be struck in the design of responsible disposal in the widest sense requires objective and practical assessment of a complex range of chemical, biochemical, engineering and economic design factors, all of which should involve the process design team in constructive dialogue with the 1 oca l regulatory authorities. In British terms, the general objective should be the Best Practicable Environmental Option. Arsenic is ubiquitous in waters, rocks and soils and all living things. Its compounds undergo natural geochemical and bi ochemi cal cycles including powerful adsorption and precipitation processes which return to nature all leakage from the inevitable disturbance of mining and extraction operations. Within limits, all life is tolerant to its presence, and adaptation and detoxication processes occur to deal with local excesses.

Jan 1, 1991