Research on Turbidity Removal and Byproduct Magnesium Hydroxide in Alkalify Flocculation Desalination Pretreatment

The reverse osmosis desalination is becoming an effective approach in seawater desalination to solve the shortage of freshwater resource. Since reverse osmosis desalination plants depend on high quality feed water to ensure. Turbidity is the most important factor of feed water of reverse osmosis desalination, and turbidity removal is a difficulty of desalination pretreatment. The alkalify flocculation desalination pretreatment technology is a cheap and effective way to reduce the turbidity of seawater. The flocculant, polyaluminiumferric chloride (PAFC), is an important additive for alkalify flocculation desalination pretreatment, and the dosage is crucial for the effect of desalination pretreatment. According to our experimental data and analysis, alkalized seawater by 9 g/L lime milk, flocculated by 9 ml/L PAFC and 3 ml/L starch solution, turbidity reduced to 0.8 NUT and meet the requirement of feed water of reverse osmosis desalination. The structure of magnesium hydroxide in floccule was regular from observed by scanning electron microscope and content improved with addition of starch from thermogravimetric analysis.