Light Metals 2007, edited by T.J. Galloway, The Minerals, Metals & Materials Society, 2007, pp. 105-112 The Conversion and Sustainable Use of Alumina Refinery Residues: Global Solution Examples Dr. Lee Fergusson Virotec Pty Ltd, 9/36-38 Newheath Drive, Arundel, QLD, 4214, Australia Keywords: Alumina Refinery Residue, Basecon Technology, Bauxsol Raw Material, Environmental Remediation, Waste Treatment Abstract This paper introduces current industry best practice for the conversion of alumina refinery residues (or “red mud”) from hazardous waste to benign, inert material. The paper will examine four neutralization methods and Basecon Technology, a sustainable conversion process. The paper will consider ways through which this converted material can be combined and processed for sustainable applications in the treatment of hazardous waste streams (such as industrial wastewater and sludges, biosolids, and CCA wastes), contaminated brownfield sites, and mine site wastes. Recent discoveries and applications, such as the successful treatment of high levels of radium in drinking water in the USA, will also be discussed. Examples of global solutions and their technical merits will be assessed. Introduction The alumina refining industry has for many years been seeking ways to minimise and reduce the environmental and social impacts of its caustic solid waste, a waste classified as “hazardous” in most countries. Such an initiative is imperative given the worldwide industry generates over 80 million dry metric tonnes of caustic waste tailings each year, with at least 30 million dry metric tonnes produced in Australia alone [1]. Moreover, recent reports from near Alcoa’s Wagerup refinery in Western Australia maintain that “residents of the nearby south-west town of Yarloop say the emissions are making them sick, causing symptoms such as nose bleeds, sore eyes and skin ulcers…There is a very long list of known toxic or carcinogenic substances which are regularly emitted [from the refinery] and yet exactly what combination it is which is making people sick…hasn’t been clearly drawn out” [2]. These concerns are even greater in less developed industrial nations, where accidental immersion in red mud has resulted in death. Alcoa has therefore recently stated: “Finding practical uses for new and stockpiled refinery residue – which has ongoing environmental and land use impacts and significant storage costs – is arguably the biggest challenge facing the global alumina industry” [3]. This paper describes some of the standard methods for neutralising caustic alumina refinery residues and considers their respective limitations. Focus will turn to the merits of Basecon Technology and its added advantage of producing a re- usable raw material which has environmental benefits. Particular attention will be given to a number of sustainable technologies which utilise this raw material in treatment solutions for industrial wastewater and solids, sewage effluent and biosolids, composting and fertiliser, and other applications. It will be shown that these applications represent a break-through in the sustainable re- classification and re-use of alumina refinery waste. Standard Alumina Refinery Waste Neutralisation Methods The production of alumina by the Bayer Process results in the creation of large quantities of caustic waste; typically two tones of red mud are produced for every one tones of alumina [1]. Alumina refineries face two choices: either store the mud indefinitely or re- use it. However, long-term storage costs and environmental liabilities are high but re-use requires some form of neutralization. Raw red mud is highly caustic (pH is usually >13.2) and there are substantial problems associated with its long-term storage, including:  The cost of constructing and maintaining containment facilities is high, and the land used for red mud storage is not available for other purposes;  Caustic red mud presents a serious threat to the health of any wildlife or humans that come in contact with it;  Preventing the escape of caustic leachate into groundwater systems, or treating any contaminated groundwater, is difficult and expensive and may need to be continued long after red mud deposition in the storage facility has ceased; and  The costs associated with public liability insurance, environmental protection, security bonds, and site rehabilitation and closure are high, and are likely to significantly increase in the future. These costs and liabilities can best be reduced by not having to store some or all the red mud. However, not having to store it requires that it is re-used in some form, and both transport and re- use applications require neutralization of the caustic component of the red mud. Natural weathering processes will eventually neutralize stored red mud, but adequate neutralization takes many decades and in the interim the problems listed above will be applicable. Thus, it is desirable to neutralize red mud in such a way that it is no longer highly caustic [4]. Several methods for achieving this objective include acid neutralization and seawater neutralization, among others. All of these strategies can be used with varying degrees of efficiency to neutralize caustic red mud and thereby wholly or partly resolve some of the storage and management problems listed above. However (with the exception of reprocessing the red mud to recover other elements, such as titanium and residual alumina and magnesium, which does not consider re-use after element recovery [5]), most re-use options that try to address red mud storage and management problems do not make use of the inherent acid neutralizing, metal binding, PO4 binding, and other unique properties of neutralized red mud. This requirement when re-using refinery residue imposes serious constraints on the selection of neutralization options. Below are five neutralization options along with their treatment limitations.