COD Reduction in Semiconductor Wastewater by Natural and Commercialized Coagulants Using Response Surface Methodology

A coagulation treatment study was conducted using both natural (sago and potato flour) and commercial (poly aluminum chloride and aluminum sulfate) coagulants in semiconductor wastewater. The effects for settling time and dosage of the coagulants as well as their interactions on the reduction of chemical oxygen demand (COD) and turbidity were investigated using a three level factorial design, Response Surface Methodology (RSM). Sago concentration showed more influence on the COD and turbidity reduction than settling time, with concentrations lower than 1.5 g L−1 giving the better reduction. The interaction of settling time and concentration on the COD and turbidity were observed when using potato starch. Concentrations higher than 1.5 g L−1 potato starch reduced the COD and turbidity better. The polyaluminium chloride and ammonium sulphate revealed that lower concentrations (0.02–1.0 g L−1) and longer settling time (30–60 min) gave the greatest reduction in COD and turbidity.