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Tikrit Journal of Engineering Sciences (2008) 15(4) 29-45
Using Aeration for Recarbonation of Water After Softening by Lime-Soda Ash
Layth Abdul-Aleem Alannaz |
Civil Eng. Dept.- University of Mosul,Iraq. |
Abstract
The research focus on using the aeration process as means for water recarbonation after lime-soda softening. The results indicated that aeration efficient for recarbonation of three water samples with different characteristics. The lime-soda softening increased the (pH) values of the three samples to reach (10.08,10.39,10.54) respectively. The aeration decreased these (pH) values to (8.26,8.36,8.23) respectively within (60)minutes. The depression was related to the convert of the hydroxide and carbonate of the sample to the bicarbonate form by CO2 gas absorbed from the air bubbles. The absorption efficiencies were (30.9,31.0,24.7)% for the three samples respectively. The research also determined the value of (pH) at which the softened sample is saturated with calcium carbonate . These values for the three samples were (8.30,8.39,8.44) respectively. Accordingly the Langer saturation index for each sample have a positive value. The samples is at supersaturation condition with calcium carbonate for all samples. Therefore the aeration period needed to obtain the saturation state at which the sample is stable was determined to be (58.8,59.1,55.2)minutes for the three samples respectively.
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Keywords: Recarbonation, Aeration, Lime-Soda Softening, Langelier Index