Nitrogen source and biomass removal effects on the performance of biotrickling filters packed with modified organisms suspended filler or volcanic rock during toluene removal

BACKGROUND: Two identical biotrickling filters, BTF1 and BTF2, were loaded with modified organisms, suspended filler and volcanic rock. The start-up times of both biotrickling filters were compared, and their performances were evaluated in terms of removal efficiency and elimination capacity. The parameters influencing the removal performance, such as the nitrogen source and biomass removal, were investigated. RESULTS: The results illustrated that both BTFs can start rapidly. In the case of BTF1, the removal efficiency was maintained at values greater than 80% when the gas flow rates ranged from 300Lh^-1 to 500Lh^-1. A change in the nitrogen source from nitrate to ammonium salt didn't markedly improve BTF1 performance, however, BTF2 removal efficiency increased from 66% to 90%. Both BTFs rapidly achieved their previous performance when the biomass was removed, and high removal efficiency greater than 90% was achieved with a variable inlet toluene concentration ranging from 0.6 gm^-3 to 1.1 gm^-3 after the biomass was removed from BTF2. Maximum elimination capacities of 135.5gm^-3h^-1 and 157.8gm^-3h^-1 were achieved with BTF1 and BTF2, respectively. An uneven biomass distribution and, compared with BTF2, a lower quantity and variety of microorganisms were observed with BTF1. CONCLUSION: These results demonstrated that when volcanic rock was used as packing material in BTFs, they exhibited higher removal efficiency and stability.