Performance and operational challenges of a full-scale reverse osmosis facility for landfill leachate treatment in Algeria.

The treatment and management of landfill leachate is challenging due to its complex and variable composition. To comply with regulations, reverse osmosis (RO) is applied as an advanced treatment for highly polluting leachate, considering its satisfying removal efficiencies. Still, operational drawbacks such as membrane fouling and concentrate management limit the full promotion of RO technology for leachate purification. This study presents the technical performance of a full-scale RO facility located at the Hamici landfill in Algeria. Leachate characteristics were assessed over 24 months from 2022 to 2023. Our work also evaluates the feasibility and limitations of RO technology, especially under high loads of organic compounds. The leachate had a high organic matter concentration, with chemical oxygen demand (COD) values ranging from 9940 to 21,500 mg L-1, 5-day biochemical oxygen demand (BOD5) from 1175 to 3666 mg L-1, and ammonia nitrogen (NH4+) levels reaching up to 3494 mg L-1. Despite the fluctuations of the leachate's quality, the RO treatment maintained consistently satisfactory abatement, about 98% for COD, 90% for BOD5, and 94% for NH4+. However, membrane fouling was recurrent due to the high pollutant load of the leachate, resulting in repetitive downtimes and membrane replacement. Extensive and costly consumption of sulfuric acid (H2SO4, 98%), up to 12,800 kg per month for pH adjustment before the RO unit, chemicals for membrane cleaning, and high energy demand were identified as the primary operational challenges in the present case study. Additionally, the hydrogen sulfide (H2S) emissions on-site and the RO's concentrate management need to be addressed to improve the sustainability of RO technology in the leachate treatment chain.