An innovative nutritional slow-release packing material with functional microorganisms for biofiltration: Characterization and performance evaluation

The type of packing material for biofiltration has a great impact on microbial growth and pollutant removal. This study evaluated the feasibility of a nutritional slow-release packing material with functional microorganisms (NSRP-FM) in a biofilter for the removal of gaseous n-butyl acetate. Through the emulsification-cross linked process and microbial immobilization, an innovative packing material was obtained, with a specific surface area of 2.45 m² g⁻¹ and a bulk density of 40.75 kg m^-3. The cumulative release rates of total phosphorus and total nitrogen were 90.6% and 75.6%, respectively, as measured while continuously spraying deionized water. To evaluate the performance of biofiltration, NSRP-FM was compared with the commercial polyurethane foam (PU-foam), in two identical biotrickling filters (BTFs). The BTF packed with the prepared NSRP-FM maintained a consistent removal efficiency (over 95%) without nutrients addition and pH adjustment. The other BTF had poor removal performance, and the removal efficiency declined to 65% when there was no pH adjustment. Energy dispersive X-ray spectroscopy (EDS) analysis of NSRP-FM showed that inorganic elements were released during the operation of BTF. The abundance of functional microorganisms suggested that the prepared NSRP-FM provided a better environment for microbial growth, despite changes in the operating conditions.