Analysis of biofilters using synthetic macroporous foam media

The removal efficiency of a pollutant being treated in a biofilter packed with macroporous units as biofilm media carriers can be maximized provided that more fouled air flows inside of the unit pieces of the media rather than around it, because the internal specific area of the carrier is several orders of magnitude higher than outside of it. A new model that accounts for the hydrodynamic distribution of a gas stream flowing inside of a macroporous packed bed, more specifically open-pore foams, is proposed. The model allows for the design of the carrier (pore size, media internal porosity, bed porosity, and external bed resistance coefficient) in the presence or absence of outer layers such as a biofilm and a liquid film so that a given pollutant removal efficiency can be attained or increased based on the amount of fouled gas flowing inside of the media rather than around it, whereas the clogging effects typically observed in the field can be avoided. The model can also be used for the special case in which the bed is packed with a monolithic open-pore carrier. Predicted values for the biofilter performance for a monolithic bed and a open-pore packed bed are in good agreement with experimental results obtained in systems treating toluene and hydrogen sulfide under a wide range (4-120 sec) of empty bed residence times and inlet concentrations (10-200 parts per million by volume).