Integrated two-stage stripping system for ammonia recovery from landfill leachate

Landfill leachate is a highly polluted effluent whose treatment is challenged by high ammonia concentrations. This study presents an integrated two-stage stripping system for ammonia recovery that reduces the need for costly and polluting alkaline chemicals. The first stage utilizes CO 2 desorption in a stirred tank to raise the leachate pH above 9, while the second stage employs a packed column for NH₃ stripping. In batch mode, CO₂ stripping successfully elevated the pH to 9 under a hydraulic retention time below 20 min at 35 °C and 1.5 vvm. The subsequent NH₃ stripping stage was optimized at a trickling liquid velocity (TLV) of 1 m·h −1 and a gas-to-liquid (G/L) ratio of 2500. While initial recovery at moderate conditions (pH 9, 35 °C) was 9.6%, chemical adjustment to pH 11 through alkali addition and 65 °C increased ammonia recovery to nearly 86%, accounting for the early NH 3 stripping during the first stage. A preliminary energy consumption cost analysis revealed that the CO₂ stripping pre-treatment dramatically improves cost-effectiveness, increasing the economic productivity from 6.14 g-NH₃/€ (using conventional NaOH) to 52.4 g-NH₃/€, a nearly ninefold improvement.