Coupling air stripping process and anaerobic digestion for the treatment of landfill leachate: organics degradation and cytotoxicity evaluation

Landfill leachate (LFL) from a controlled discharge in Tunisia was found to be highly loaded with ammonia. This study investigated the feasibility of an air stripping process aiming to mitigate the inhibitory effect of ammonia. Optimization of this process, using an orthogonal central composite design, intended to reduce the ammonia concentration and also to fix it in a safe range for the subsequent anaerobic process. Optimization showed that, to remove 60% of ammonia, pH, air flow rate, and reaction time should be fixed at 10.8, 6 L min−1, and 18 h, respectively. The air stripping process improved the anaerobic digestion (AD) of leachate in an upflow anaerobic fixed bed reactor. Chemical oxygen demand (COD) removal efficiency exceeded 80% at an organic loading rate (OLR) of 1.3 g COD L−1 day−1. Analysis of the organic compounds monitored by gas chromatography coupled to mass spectrometry (GC–MS) showed that contaminants were efficiently removed after the anaerobic process. Cytotoxicity was significantly reduced subsequent to the air stripping and anaerobic process.