Research
Effect of Chemical Pretreatment on the Seawater Fouling Potential
In this research, three pretreatment chemicals, ferric chloride, aluminum chloride, and powdered activated carbon, were applied at different concentrations to a raw seawater feed. Five different concentrations (2, 5, 10, 15, and 20 ppm) of each chemical were used to examine the effect on reducing the silt density index (SDI) of raw seawater. The best overall reduction in SDI, 10.05, was obtained with ferric chloride at a concentration of 10 ppm. At higher concentrations of ferric chloride, the SDI did not improve and instead increased. The same behavior was observed with powdered activated carbon (PAC), where a higher concentration resulted in a higher SDI. The SDIs of seawater treated with 2 and 20 ppm aluminum chloride were almost the same – 12.7 and 12.1, respectively. The study shows that using higher concentrations of chemical coagulant may produce adverse results rather that improving the SDI of seawater. Chemical pretreatment should be optimized according to the type and quality of the feed water.
