| Abstract
| - Biofilms cultivated on oxygen-filled gas-permeablemembranes grow differently than conventional biofilms,as the chemical species required for growth diffuse fromdifferent sides of the biofilm. Oxygen is delivered directlyto the base of the biofilm by the membrane, while organicsubstrates and other soluble nutrients are provided tothe upper surface of the biofilm via the water in which themembranes are immersed. This counterdiffusion ofnutrients results in a growth environment very differentfrom that of conventional biofilms that receive both oxygenand other nutrients from the water. In recent years,membrane-supported biofilms have been shown tosimultaneously remove chemical oxygen demand (COD)and inorganic nitrogen from wastewater in laboratory studies.Several investigators have developed computer modelsof these biofilms, but they have all focused on a singlepopulation of aerobic bacteria. While these models are usefulin characterizing the behavior of these biofilms in purecultures, they are not useful in modeling the behavior ofthe biofilms in mixed cultures such as those found inwastewater treatment. In this study, a multipopulation biofilmmodel was developed that includes aerobic heterotrophs,nitrifiers, denitrifiers, and acetoclastic methanogens.The model was constructed with Aquasim software andcan predict the COD and inorganic nitrogen removal behaviorobserved previously in experimental studies. In thispaper we present examples of predicted biofilm behaviorand compare the results of this multiple-populationmodel with the single-population models published previously.In addition, the behavior of the biofilm is discussed interms of application to wastewater treatment.
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