Silica removal during lime softening in water treatment plant

Silica, SiO2, is typically found in well water supplies. Most of the silica found in well waters is a result of dissolving silica-containing rock. Silica content in brackish water is generally in the range of 20 to 60 ppm. In Salbukh water treatment plant, silica concentration of raw water is about 30 ppm. High concentration of silica causes membrane fouling in the reverse osmosis units. During lime softening process calcium and magnesium are precipitated. Calcium is deposited as calcium carbonate while magnesium is deposited as magnesium hydroxide. Upon precipitation, magnesium hydroxide forms larger floc that more readily adsorbs or entraps silica particles in the water. So silica will be removed with the precipitation of magnesium hydroxide in the lime softening by adsorption on the magnesium precipitates. In this paper, silica concentrations of raw water and softened water will be monitor during the softening process in Salbukh water treatment plant. Measurements of silica content of softened water will be performed at different pH level in the precipitator. The effect of lime concentration on silica removal during softening was investigated