The study focused on treating leachate from a landfill in Sungai Petani, Kedah. Researchers used solid waste to remove color, COD, SS, and heavy metals from the leachate. By recycling the leachate through the solid waste, they found that a two-hour detention time was most effective, resulting in significant removal percentages: SS up to 60.9%, COD up to 76.2%, and Color up to 46.9%. Interestingly, the removal of Cr and Zn was not affected by the detention time.