Bioclogging of biofilters and unsaturated porous media

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Biofilters are used to treat a wide variety of contaminated wastewater and air streams. They are operated under unsaturated conditions to ensure that there is sufficient oxygen available for the aerobic degradation of the organic compounds to be removed from the waste streams. In the case of wastewater filters the organic materials are present in the dissolved phase or as suspended solids. The treatment of air streams relies on the partitioning of the organic compounds between the air and aqueous phases as the air moves through the filter. In both cases, the microbial population, which resides in the aqueous phase and/or attached to the solid phase, breaks down the contaminants of concern into less harmful products. The waste stream provides a continuous food source for the microorganisms causing the biomass within the pore spaces of the filter to increase. Excessive build up of biomass will impact the operation and service life of the filter and may eventually lead to complete clogging and failure of the filter. Very few models exist that simulate the hydraulics and processes occurring within biofilters. The filter is often treated as a "black box" and the hydraulic and organic loading adjusted to establish the optimal loading conditions. However, any time a new waste stream or a new filter media is considered, similar "black box" experiments must be conducted. The overall goal of this research proposal is to better understand the processes occurring within the biofilters such that conceptual and numerical models can be developed to assess the potential performance of a biofilter, reducing the need to conduct numerous "black box" experiments to determine the ideal size and operating conditions of that filter medium. The knowledge gained and the models proposed herein will allow manufacturers and designers of biofilters to evaluate alternate biofilter media, to effectively design and size new biofilters, and to evaluate and optimize operating conditions to increase the service life of these filters.