Microbial community in a pilot-scale biotrickling filter with cell-immobilized biochar beads and its performance in treating toluene-contaminated waste gases

Cell-immobilized bamboo-biochar beads (cell-biochar beads) that were made of an environmentally friendly material were used as packing material in biotrickling filters (BTFs). Cell-biochar beads play the double role of an adsorber of pollutants and a carrier for the growth of attached bacteria, increasing the efficiency of pollutant removal by BTFs. A toluene removal rate of over 99% was achieved. The best organic loading rate (OLR) of BTF on toluene was 46.2 g m⁻³ h⁻¹ and its elimination capacity (EC) was 34.9 g m⁻³ h⁻¹ at an exhaust gas flow rate of 0.015 m³ min⁻¹ and an empty bed residence time (EBRT) of 99 s. According to a microbial community analysis, when the cell-biochar beads were immobilized with a targeted pollutant-degrader under various operating conditions, they were dominated by microbes, revealing that the beads had mitigated the inhibition effect of substrate on biodegradation. Therefore, when cell-biochar beads are used as a packing material in a BTF, the exhaust gas can be effectively treated; the impact of the organic load can be effectively buffered and the EC can be improved by scaling up.