Effect of inoculum size on the rates of whole ore colonisation of mesophilic, moderate thermophilic and thermophilic acidophiles

摘要

Bioheap leaching of low grade copper sulphides has been applied successfully commercially for the extraction of copper from secondary sulphide minerals. Industrial heaps could reach tens of meters in height and kilometers in width, hence inoculation of the heaps remains an important process parameter to minimise residence time required for the heap and to maximise extraction. Thermophilic bioleaching for leaching of chalcopyrite poses an additional challenge of rising temperatures inside the heap that impact the microbial population. After heap start up, rising heap core temperatures make conditions less favorable for mesophilic microbial species, and the moderately thermophilic community enters as the next in succession in the consortium. In turn, thermophilic microorganisms succeed the moderately thermophilic microbes as thermophilic temperatures are reached. A detailed understanding of the microbial colonisation of whole ore at temperatures specific to the microorganisms involved in bioleaching is necessary to optimise microbial succession during thermophilic bioleaching. The bulk of published research is focused on microbial growth rates of bioleaching organisms in liquid cultures, and little work has been conducted on understanding microbial colonisation of whole ore. To extend the information available on the microbial diversity and succession in a bioleaching habitat, a study of bioleaching microbes that are known to colonise the ore body is required. The aim of this work was to explore aspects of colonisation of low grade chalcopyrite ore at 231 , 501 and 65°C by acidophilic chemolithotrophic microorganisms. Laboratory column packed bed reactors were designed to simulate heap leach environments and to provide a systematic way of studying microbial dynamics on whole ore. Different inoculum sizes and inoculation strategies were investigated across mesophilic, moderately thermophilic and thermophilic conditions and the effect on effluent Eh, pH and iron levels are discussed.