Effect of Coagulant/Flocculant Dosage and pH to Water Recovery of Black Liquor Wastewater in Bioethanol Production from Oil Palm Empty Fruit Bunch Using Response Surface Methodology

Coagulation and flocculation process was used to treat black liquor wastewater from alkali pretreatment of bioethanol production from oil palm empty fruit bunch. The optimization and the effect of pH, coagulant and flocculant dosage against decolorization, TSS reduction, final pH and sludge volume were investigated using Response Surface Methodology (RSM). Six combination were used, however, no combination gave good result to all four responses. Decolorization percentage of 99.69% was obtained by the combination of PAC and anionic polyacrylamide. The combination of alum and anionic polyacrylamide gave 91.12% TSS reduction. Final pH of 7.3 was resulted also from the combination of PAC and anionic polyacrylamide While, 50 ml sludge volume was generated from the combination of PAC and anionic polyacrylamide. From RSM with Central Composite Design (CCD) analysis, strong interaction between coagulant dosage and pH revealed to be the significant factor for black liquor wastewater treatment.