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Investigation of sulphide oxidation kinetics and impact of reactor design during passive treatment of mine water
Expanded Title:Mine wastewaters generated during active mining operations or resulting from groundwater rebound at abandoned sites will have major environmental and economic implications for South Africa in the medium and longer term, particularly as active dewatering of some underground basins ceases. Active chemical treatment of the wastewaters, involving oxidation, neutralisation and sedimentation, is the most widely employed technology. Recently there has been increasing interest in passive biological treatment processes. Biological sulphate reduction is a well understood and efficient process and has been incorporated into a number of full scale treatment systems. Sulphate in acid mine drainage (AMD) streams is typically derived from the oxidation of pyrite (FeS2) resulting in a stoichiometric excess of sulphate relative to metals. As a result, even if the biological treatment system incorporates a metal sulphide precipitation step there will be a surplus of sulphide, from the sulphate reduction step. Hydrogen sulphide gas has an unpleasant odour at low concentrations and is extremely toxic at higher concentrations. Therefore, sulphide oxidation is a key step in the development of a successful biological treatment process. Two units of the IMPI process were simulated at the Department of Chemical Engineering at the University of Cape Town. Two reactors were operated as saturated upflow systems. Three linear flow channel reactors were designed and purpose built. Several analytical techniques were developed and optimised to facilitate the measurement of a range of sulphur species, including ploysulphides, and allow a complete sulphur mass balance to be closed. The results illustrate the relationship between organic carbon flux, biofilm formation and efficient partial sulphide oxidation to elemental sulphur. Scanning electron microscopy, with electron dispersive x-ray analysis, showed the presence of discrete sulphur globules, embedded in a matrix consisting of some organic matter, but substantial chemical precipitates. The data highlighted the importance of organic carbon flux through the integrated system. Sufficient organic carbon is required to sustain a stable biofilm, which is necessary to prevent the sulphide from being oxidised back to sulphate.
Date Published:30/06/2011
Document Type:Research Report
Document Subjects:Mine water - Mine water treatment
Document Keywords:Ground Water
Document Format:Report
Document File Type:pdf
Research Report Type:Consultant
WRC Report No:KV 268/10
ISBN No:978-1-4312-0102-0
Authors:Van Hille RP; Mooruth N
Project Leader:van Hille RP
Project No:K8/941
Document Size:2 210 KB
Attachments:EXECUTIVE SUMMARY KV 268.pdf
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