A Decade of Designing Biological Nutrient Removal (BNR) Processes for Landfill Leachate Treatment: Challenges & Lessons Learned

This paper presents some of the key design considerations and lessons learned from designing and operating landfill Leachate Treatment Facilities (LTFs) based on a decade of experience with numerous landfill leachates. Landfill leachate treatment is a major challenge due to the high and variable contaminant concentrations such as high COD, extremely high ammonia levels, and significant Total Dissolved Solids (TDS) concentrations. Biological Nutrient Removal (BNR) technology, more specifically, the Anoxic/Oxic processes have been implemented in order to achieve nitrification and denitrification and reduce the oxygen demand. Due to high variability of organics-to-nitrogen ratio, the LTFs were designed for long HRTs of 2 to 3 days. Anoxic/oxic processes without pre-treatment for removal of inorganics have been successfully adopted. High TDS concentrations of 11,000 mg/L did impair nitrification. Proper characterizations of leachate, backed by treatability or pilot studies are essential to select a reliable LTF that can effectively accommodate variable influent characteristics.