Factorial Design and Optimization of Landfill Leachate Treatment Using Tannin-Based Natural Coagulant

In this study, tannin-based natural coagulant was used to treat stabilized landfill leachate. Tannin modified with amino group was utilized for the treatment process. Central composite design (CCD) was used to investigate and optimize the effect of tannin dosage and pH on four responses. The treatment efficiency was evaluated based on the removal of four selected (responses) parameters; namely, chemical oxygen demand (COD), color, NH(3)–N and total suspended solids (TSS). The optimum removal efficiency for COD, TSS, NH(3)–N and color was obtained using a tannin dosage of 0.73 g at a pH of 6. Moreover, the removal efficiency for selected heavy metals from leachate; namely, iron (Fe(2+)), zinc (Zn(2+)), copper (Cu(2+)), chromium (Cr(2+)), cadmium (Cd(2+)), lead (Pb(2+)), arsenic (As(3+)), and cobalt (Co(2+)) was also investigated. The results for removal efficiency for COD, TSS, NH(3)–N, and color were 53.50%, 60.26%, and 91.39%, respectively. The removal of selected heavy metals from leachate for Fe(2+), Zn(2+), Cu(2+), Cr(2+), Cd(2+), Pb(2+), As(3+) and cobalt Co(2+) were 89.76%, 94.61%, 94.15%, 89.94%, 17.26%, 93.78%, 86.43% and 84.19%, respectively. The results demonstrate that tannin-based natural coagulant could effectively remove organic compounds and heavy metals from stabilized landfill leachate.