Semiconductor Wastewater Treatment Using Tapioca Starch as a Natural Coagulant

Abstract

The efficiency of using tapiocastarch as a natural coagulant on semiconductor wastewater treatment wasinvestigated. The silica content in the wastewater was pH dependent and it was found that the reduction of COD and turbidity occurredat pH between 12 and 14 with measurements below 100 mg/L and 100 NTUrespectively. A three-level factorial designexperiment in the Response Surface Methodology (RSM) was applied to determinethe influence of retention time and dosage of the tapioca starch. Theparameters studied were chemical oxygen demand (COD), turbidity and totalsuspended solids (TSS). The R2 for turbidity, COD and TSS were 0.92,0.92 and 0.77 respectively. Results indicate that the dosage of the tapiocastarch has a higher influence on COD and turbidity reduction. Tapioca starch asa natural coagulant has shown that the optimum turbidity reduction was 99% at asettling time of 30 minutes with dosage of 0.1 g/L. The COD reduction wasachieved at 87% after 60 min of retention time and 0.1 g/L of dosage whilehigher coagulant dosages reduced the TSS concentration to 10.9 mg/L atretention time between 50 to 60 minutes.