The use of desalination technologies which produce concentrated brines is acutely limited by inadequate waste brine disposal mechanisms such that the brine does not contaminate fresh water resources. The treatment of highly saline brine using freeze desalination technique trade marked as HybridICE TM technology was investigated at pilot scale. The capacity of the HybridICE TM process to generate fresh water by freeze desalination of brine was investigated in this study. Brine samples to feed into the HybridICE process unit were prepared in tanks with volume capacities between 1.0 and 10.0 m 3 by dissolving common salt into tape water. The effects of refrigerant temperature, initial brine concentration, energy consumption were evaluated in relation to product ice quality. Feed brine samples were processed in batches in a closed system where it was continuously re-circulated to generate product ice and more concentrated residual small volume of brine stream. The quality of ice produced could be turned into potable water it terms of its low total dissolved salts and conductivity. The salt removal, based on the average chloride concentration in the ice samples, was 96 %. The energy utilization efficiency amounted to an average of ZAR 10.0/m 3 water assuming energy cost of ZAR 0.39/kWh. The HybridICE TM technology was shown to be a better option than other desalination technologies currently in use, in terms of energy utilization and cleaner byproducts.

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Freeze desalination is an alternative method for the treatment of mine waste waters. HybridICE(®) technology is a freeze desalination process which generates ice slurry in surface scraper heat exchangers that use R404a as the primary refrigerant. Ice separation from the slurry takes place in the HybridICE filter, a cylindrical unit with a centrally mounted filter element. Principally, the filter module achieves separation of the ice through buoyancy force in a continuous process. The HybridICE filter is a new and economical means of separating ice from the slurry and requires no washing of ice with water. The performance of the filter at a flow-rate of 25 L/min was evaluated over time and with varied evaporating temperature of the refrigerant. Behaviours of the ice fraction and residence time were also investigated. The objective was to find ways to improve the performance of the filter. Results showed that filter performance can be improved by controlling the refrigerant evaporating temperature and eliminating overflow.

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The HybridICE technology operates on the principle that growing ice crystals reject impurities during freezing and is a "zero liquid discharge" process, whereby the water is completely isolated from the dissolved waste species. The technology recovers water from waste waters for re uses for all purposes. The process allows the utilisation of both surplus process heat and cooling energy. The waste heat from the refrigeration cycle is, moreover, utilised for vacuum evaporation to recover a fraction of the water as condensate. The predominant water fraction is recovered by isolating the ice from a concentrated process brine stream. The process takes place in a static concentrator, known as the HybridICE Filter module (HIF) that separates the suspended ice crystals from the concentrated brine slurry to recover ice crystals as pure water. The recovered ice from the freeze crystallisation does not require rinsing with fresh water. Basic factors influence the quality and yield of recovered water. These include but are not limited to: TDS of the waste water stream; first ice point; ice content of the process waste water; mass-flow. The slurry ice feed stream was generated using the HybridICE freeze crystallisation plant. The objective was to establish the comparative behaviour of a low and high sodium chloride feed using 2% and 8% (m/m) NaCl feed brine streams.