The study focused on using waste cockles shells to improve the treatment of leachate from a landfill in Pulau Burung, Pulau Pinang. The shells filter out organics before further treatment. The attached growth process under semi-anaerobic conditions effectively reduced BOD, COD, VSS, SS, temperature, pH, and conductivity in the leachate. After 35 days, the removal of VSS, SS, and BOD was significantly better. This method not only enhances leachate treatment but also recycles waste materials, saving costs and promoting sustainability.