Abstract: Water and wastewater treatment activities, projects and capabilities of South African environmental engineering specialist Envig are detailed. The company, as part of the Weir Wesgarth Consortium, has pre-qualified for the major Namibian Water Supply Project, one of the largest of its kind to date in southern Africa. This project involves the desalination of seawater to meet increasing water demand and shortfalls. Envig, if awarded the contract, would be involved in construction of three or four reverse osmosis or mechanical vapour compression sea water desalination plants and associated infrastructure. The company is also involved in a mine water desalination project at the Eskom Tutuka Power Station. A reverse osmosis plant using low fouling maintenance is being installed to deal with acid mine drainage water. Details of the design and operation of this plant are given.

Abstract: ERWAT's Ancor Wastewater Treatment Works on the Far East Rand commissioned a 10 Ml/day full-scale plant to treat toxic mine-water from the Grootvlei gold mine using primary sewage sludge. The R15-million plant is treating sulphate rich acid mine drainage using the Rhodes BioSURE Process. First, the pumped mine-water is treated at a high-density separation (HDS) plant to remove iron and condition pH levels. Then it is pumped two km via a newly-constructed 10 Ml capacity pipeline to the Ancor works. This mine-water is then mixed together with primary sewage sludge in a mixing tank from where a splitter box directs the material to eight biological sulphate reducing reactors or bioreactors. The overflow water which is rich in sulphide is pumped through the main pump station to another mixing box. Here, iron slurry is mixed with the material before it is again divided between four reactor clarifiers for sulphide removal. The overflow water, now containing reduced sulphate levels and virtually no sulphide is pumped to Ancor's biofilters for removal of remaining Chemical Oxygen Demand (COD) and ammonia following the conventional sewage treatment process for eventual release into the Blesbokspruit.

Abstract: Environmentally compatible Waste Management schemes employed by the European extractive industry for the development of new projects, and applied in operating sulphide mines, are presented in this study. Standard methodologies used to assess the geotechnical and geochemical properties of the solid wastes stemming from mining and processing of sulphidic metal ores are firstly given. Based on waste properties, the measures applied to ensure the environmentally safe recycling and disposal of sulphidic wastes are summarised. Emphasis is given on the novel techniques developed to effectively prevent and mitigate the acid drainage phenomenon from sulphidic mine wastes and tailings. Remediation measures taken to minimise the impact from waste disposal sites in the post-closure period are described.