Process Performance of a Biotrickling Filter Using a Flow-Directional-Switching Method

Non-uniform distribution of biomass and the accumulation of excess biomass at the inlet of a unidirectional flow biotrickling filter (UF-BTF) may lead to severe operating problems including increasing airflow resistance in packed bed, clogging, and low contaminant removal efficiencies, even performance loss. Therefore, a flow-directional-switching biotrickling filter (FDS-BTF) was designed to improve performance such as the maximum elimination capacity and elimination efficiency. Toluene was chosen as the unique carbon source for microorganism. The results indicated that the purification performance of FDS-BTF was superior to UF-BTF. The maximum elimination capacity of FDS-BTF was up to 480g/(m3h), which was 17.1% higher than that of UF-BTF. After a 50-day continuous operation, FDS-BTF attained the stable purification performance and the outlet concentrations of toluene could meet the emission standard with inlet concentrations ranging from 720 to 1100mg/m3 for an empty bed residence time (EBRT) of 23.9s. The average well color development in FDS-BTF was higher than that in UF-BTF. It indicated that FDS-BTF could improve the metabolic activity, which may improve the uniform distribution of biomass along the length of packed bed. When two systems were shut down, 24 and 48h, respectively, the time that FDS-BTF and UF-BTF needed to restore the former elimination efficiency after a shut down of 48h were 3-4 and 9-10h. These data indicated that the purification performance of FDS-BTF was superior to UF-BTF.