Conventional desalination technologies such as electrodialysis reversal and reverse osmosis cannot be directly used to economically treat those waters encountered in the South African gold mining industry which are scaling with regard to calcium sulphate. The Chamber of Mines of South Africa Research Organisation therefore decided, in the early 1980's, to undertake research into the development of seeded reverse osmosis technology for treating scaling mine waters. This research culminated in the development of foe Slurry Precipitation and Recycle Reverse Osmosis (SPARRO) technology. Extensive pilot plant investigations were undertaken and it was shown that the SPARRO process is technically capable of producing a high quality product water at water recoveries of around 95 per cent. Problems were encountered, however, with fouling of the tubular cellulose acetate membranes, resulting in declines in the flux rate. It is postulated that the fouling is mainly due to the presence of quartzitic suspended material, although the mechanism of fouling cannot be explained. Further research is being undertaken to clarify the potential fouling mechanisms and to optimize the membrane cleaning regimes. The capital cost for a 46.3 1/s (4Ml/d) SPARRO plant has been estimated at R16.2 million, with an estimated operating cost of R 1.48/m3 of product water.

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