From Prediction to Remediation: Characterization of Tropical Landfill Leachates Using ARIMA and Application of Adsorption and Reverse Osmosis Treatments

Landfill leachates in tropical regions represent a critical environmental challenge due to their complex composition and pronounced seasonal variability. This study sought to characterize leachates from a tropical landfill in Valledupar, Colombia, and to evaluate advanced treatment technologies for the removal of organic pollutants. An ARIMA (3,0,3) model was implemented on an eight-year time series (2016–2023) of leachate flow data to identify seasonal patterns and support hydraulic load forecasting. Physicochemical characterization was conducted following APHA standard methods, which revealed high levels of COD, BOD5, chlorides, and lead. Two treatment technologies were assessed independently: (i) adsorption using granular activated carbon in batch and continuous-flow systems, under 36 experimental conditions that combined pH levels (2–7) and carbon dosages (20–120 g); and (ii) reverse osmosis employing polyamide membranes operated at 18 bar and at pH values of 6.0, 7.0, and natural (unaltered) conditions. The results confirmed that leachate generation exhibits clear seasonal variability correlated with rainfall patterns. The Langmuir isotherm demonstrated the best fit at pH 4.0 (R2 = 0.9685), and the continuous system achieved 97% COD removal within 90 min. Reverse osmosis consistently removed over 94% of COD and BOD5 across all pH conditions. These findings highlight the value of integrating time-series forecasting with optimized treatment technologies to support effective and adaptive leachate management strategies in tropical environments.