Performance Evaluation of Lab-Simulated Bioreactor Landfills under Aerobic and Anaerobic Conditions Using Wastewater and Sludge as Moisture Sources

Abstract

This study examined the effects of introducing wastewater and sludge, together with leachate recirculation, on the decomposition of municipal solid waste (MSW) in bioreactor landfills under controlled moisture conditions. To achieve this, three lab-simulated bioreactor studies were conducted under aerobic (AER) and anaerobic (AN-1 and AN-2) conditions to examine the influence of these moisture sources on the rate of stabilization. Anaerobic bioreactor AN-1 was operated with wastewater, while AN-2 was operated by adding sludge and wastewater. A comprehensive monitoring of settlements, gas generation, leachate quality, temperature, and moisture was carried out throughout the operational period for all the bioreactors. From the experiments, it was observed that the change in COD and BOD concentrations became relatively slow after 150 days in AER, 330 days in AN-1, and 300 days in AN-2. The biogas production in AN-2 began previously than in AN-1 due to the utilization of sludge and wastewater, which provided additional nutrients for enhancing the microbial activity to break down the waste. The stabilization of MSW showed high effectiveness in AER, with 95% of settlements and approximately 90% of gas yield occurring within 150 days of operation. The average surface differential settlements of 131.5, 102.6, and 119 mm, representing 32.9%, 25.7%, and 29.8% relative to the initial height of MSW, were observed in AER, AN-1, and AN-2, respectively. Carbon, hydrogen, and nitrogen analyses were conducted on both fresh and degraded samples. The results revealed a 10% greater reduction in carbon in AN-2 compared to AN-1, attributed to the addition of 10% sludge to wastewater and leachate. The highest volatile solids removal of 59.1% was observed in AER, followed by AN-2 with 55.5% and AN-1 with 50.6%. Water scarcity has emerged as a significant global issue, making it crucial to explore alternative water sources to operate bioreactor landfills. This study explores the potential integration of wastewater and sludge, alongside leachate recirculation, to meet the substantial moisture requirements in bioreactor landfills. These practices can enhance landfill stabilization processes by accelerating the digestion of municipal solid waste under controlled moisture conditions. The findings of this research offer a practical framework for optimizing landfill operations by monitoring key parameters such as leachate composition, gas production, temperature, moisture content, and settlement behavior. Integrating wastewater and sludge into landfill processes not only reduces reliance on conventional water sources but also offsets the high treatment costs of these materials. Additionally, the captured biogas can be refined into a sustainable energy source, contributing to energy recovery objectives. These results have significant implications for modern landfill management by promoting the dual benefits of waste stabilization and resource recovery. The outcomes of this study may help upgrade current landfill management practices by integrating wastewater and sludge into landfill operations.