Treatment of Landfill Waste, Leachate and Landfill Gas: Modelling/Simulation and Experimental Studies

Landfilling has been relegated to containing waste and hoping for minimal environmental impact. However, landfills produce harmful leachate and landfill gas that require treatment. To speed up the landfill biodegradation process, aerating the landfill to promote aerobic biodegradation has been implemented successfully. However, the conversion from a traditional anaerobic landfill to an aerobic landfill is to this point, not well researched. A 3-dimensional dynamic mathematical model was developed that depicts the conversion of a landfill from an anaerobic to an aerobic operation. The results of the model (CO2 volume fraction and temperature), agreed with data from published work. The model solved for the liquid and gaseous pressures/velocities, gas composition, anaerobic/aerobic biomass concentrations and temperature; all were solved with respect to space and time. Landfill leachate requires treatment before release and landfill gas requires purification (removal of CO2) before it can be used as a fuel. A hybrid sorption (absorption and adsorption/ion exchange) system was developed to treat leachate and purify landfill gas in the same column. The absorption results showed that leachate could remove more carbon dioxide from the landfill gas than pure water, due to its slight basicity. The adsorption/ion exchange results showed that lead could be removed from model leachate but not below Ontario discharge guidelines with the length of the column used (50-55 cm zeolite bed height)

Application of Nanosize Zeolite Molecular Sieves for Medical Oxygen Concentration

The development of a portable oxygen concentrator is of prime significance for patients with respiratory problems. This paper presents a portable concentrator prototype design using the pressure/vacuum swing adsorption (PVSA) cycle with a deep evacuation step (−0.82 barg) instead of desorption with purge flow to simplify the oxygen production process. The output of the oxygen concentrator is a ~90 vol % enriched oxygen stream in a continuous adsorption and desorption cycle (cycle time ~90 s). The size of the adsorption column is 3 cm in diameter and 20 cm in length. A Li+ exchanged 13X nanosize zeolite is used as the adsorbent to selectively adsorb nitrogen from air. A dynamic model of the pressure and vacuum swing adsorption units was developed to study the pressurization and depressurization process inside the microporous area of nanosized zeolites. The describing equations were solved using COMSOL Multiphysics Chemical Engineering module. The output flow rate and oxygen concentration results from the simulation model were compared with the experimental data. Velocity and concentration profiles were obtained to study the adsorption process and optimize the operational parameters