Elevated levels of contaminants, such as organic chemicals, nitrogen, phosphorus, and heavy metals, are present in landfill leachate and pose serious dangers to both human health and the environment. The main objectives of this study were to evaluate the presence of heavy metals and characterize the leachate from the Oulad Berjal landfill in Kenitra. It also aimed to compare the effectiveness of leachate treatment using coagulation combined with filtration (using red brick waste as the filter material) and coagulation alone. The originality of this work lies in its treatment of leachate for the first time, combining filtration with red brick waste and coagulation. The combination of these two processes for leachate treatment has never been addressed in the literature. The efficacy of a coagulation-filtration method for red brick waste was assessed. The results showed that the leachate from the Kenitra landfill had significant metal contamination. With concentrations of 1.08 mg/L and 100 mg/L, respectively, Cr and Zn are the most concentrated metals. The concentrations of Pb and Cu are moderate, ranging from roughly 0.45 to 0.79 mg/L and 0.35 to 0.70 mg/L, respectively. Ni was present at an intermediate concentration of about 0.07 to 0.32 mg/L, while Cd remained low at 0.03–0.05 mg/L. When the leachate was treated by coagulation followed by filtration, COD, ammonium, turbidity, and heavy metals were significantly reduced. Coagulation-flocculation, which eliminated 81% of COD, 65% of NH₄⁺, 83% of Pb, and 70% of Cr, was primarily responsible for the reduction. Filtration greatly reduced turbidity (71%), COD (50%), and ammonium (31%), further improving the treatment. Because of its high porosity and specific surface area, the discarded red brick can absorb and filter sewage.