Simultaneous effects of airflow and temperature increase on water removal in bio-drying

Bio-drying MBT is a type of mechanical biological treatment (MBT) system, whereby the aerobic biological process is first used to remove moisture, which is followed by the mechanical separation to recover material and energy as a solid recovered fuel (SRF). Among various parameters of this process, the simultaneous effects of airflow rate and organic contents were examined in this study. A 25 L acrylic column reactor was filled with simulated waste. Temperature and humidity of the air inlet and outlet were continuously monitored, and CO₂ concentrations in outlet air were periodically analyzed to observe aerobic biodegradation as well as metabolic water generation. Based on the data, the different water removal contributions by airflow and biodegradation were compared, and finally, evaluation of the inter-dependence of parameters and feedback effect in the bio-drying process was carried out. While the biodegradation of organics induced a significant amount of water removal due to increased temperature, high organic content has a negative effect on water removal by generating metabolic water. Water removal by air replacement is greater than that associated with temperature increases caused by biodegradation. However, excessive airflow rate can terminate biodegradation by drastically lowered moisture content, even though organics remained.