Performance evaluation of biofilters packed with carbon foam and lava for nitric oxide removal.

Long-term (>8 months) results of nitric oxide (NO) removal in biofilters, respectively, packed with lava and two different pore sizes of carbon foam (24 pores/cm (PPC) and 18 PPC) were measured. During the operation, NO removal efficiency, pressure drops, pH dependence and removal profile were evaluated. NO removal efficiencies were above 93.8%, 79.4% and 58.6% in the biofilters, respectively, packed with 24 PPC carbon foam, 18 PPC carbon foam and lava. The lava-packed biofilter demonstrated higher buffer capacity for change of pH. However, with sufficient nutrient and buffer solution feeding, the biofilter packed with carbon foam showed a higher NO removal efficiency. The pressure drops of the biofilter packed with carbon foam did not exceed 11 mm H(2)O/m. The low-pressure drops made it possible by using carbon foam as packing to conveniently prevent the clogging and channeling problems associated with conventional biofilter operations.