Ethylbenzene removal under mesophilic conditions in a multiple-stage biofilter with macadamia nutshells as carrier material

A biofilter was used to treat air polluted with ethylbenzene. Macadamia nutshells, which are a cheap waste product in Thailand, were chosen as the packing material for the biofilter. The moisture content (6.6 w%), water holding capacity (16.8 w%), nutshell density (1.3 g ml) and organic content (78.0 w%) of the macadamia nutshell were measured. The biofilter was operated during 5 months, in which several inlet loads (IL), empty bed residence times (EBRT) and temperatures (T) were applied. At a T of 303 ± 2 K removal efficiencies (RE) higher than 90 % were obtained for IL lower than 95 g m h and 85 g m h at EBRTs of 150 and 90 s, respectively. The estimated yield coefficient, determined from the carbon dioxide production, resulted in 0.79 g dry biomass per g of ethylbenzene (EB) degraded. The results illustrate that a biofilter with macadamia nutshells as carrier material is a good option for air treatment at temperatures from 298 to 308 K. In the mesophilic area, the performance of the biofilter will higher with a higher temperature.