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ROIFA-5 Model for Predicting Total Hardness Fouling Flux and Saturation Factors on the RO Membrane |
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PP: 17- 28 |
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Author(s) |
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Azza. I. Hafez,
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Abstract |
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| Based on the earlier dehydration model, the reverse osmosis inorganic fouling assessment model (ROIFA-5) and spreadsheet has been developed for predicting the inorganic fouling flux on the RO-membrane surface used for desalination and wastewater treatment at any desired recovery rate. Several important outputs could be obtained from the application of this spreadsheet, among them; the probable dissolved salt combination, total hardness fouling flux (THFF), silica fouling potential, molar ratios, total brine fouling load, wt/wt% of different hardness molecules, chemical composition of the resulted brine and saturation factor (SF%) for calcite and gypsum. In addition, some other useful information is obtained like: brine osmotic pressure, mechanical pressure, brine ionic strength, brine ion product (IP) of calcite and gypsum. Both SF and IP output have been estimated according to the saturation model based on the obtained upper solubility level of calcite and gypsum under variable chloride natural waters, and not on their solubility in pure water as considered in thermodynamics. It has been found that the solubility of carbonate and sulfate mineral salts are relatively increasing with the increase of chloride content (or probably NaCl) and follows natural tight rules. It is proved that the inorganic fouling potential is proportional to the brine total hardness fouling flux (THFF) and not its gross salinity. In many investigated cases the lower salinity water may acquire higher hardness fouling potential than the higher salinity water that may contain less dissolving hardness, like ocean water. The ROIFA program had been subjected to many laboratory tests and field investigations and was found satisfactory. This software is free for all and available upon request. |
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