Modeling the effects of biomass accumulation on the performance of a biotrickling filter packed with PUF support for the alkaline biotreatment of dimethyl disulfide vapors in air

Abstract

Excess biomass buildup in biotrickling filters leads to low performance. The effect of biomass accumulation in a biotrickling filter (BTF) packed with polyurethane foam (PUF) was assessed in terms of hydrodynamics and void space availability in a system treating dimethyl disulfide (DMDS) vapors with an alkalophilic consortium. A sample of colonized support from a BTF having been operating for over a year was analyzed and it was found that the BTF void bed fraction was reduced to almost half of that calculated initially without biomass. Liquid flow through the examined BTF yielded dispersion coefficient values of 0.30 and 0.72 m2 h-1, for clean or colonized PUF respectively. 3D images of attached biomass obtained with magnetic resonance imaging allowed to calculate the superficial area, the volume percentage and the biofilm depth as 650 m2 m-3, 35% and 0.6 mm respectively. A simplified geometric approximation of the complex PUF structure was proposed using an orthogonal 3D mesh which predicted 600 m2 m-3 for the same biomass content. With this simplified model it is suggested that the optimum biomass content would be around 20% of bed volume. Biofilm activity was evaluated by respirometry and biological intrinsic kinetics could be described with a Haldane equation type. Experimentally determined parameters were used in a mathematical model to simulate the DMDS elimination capacity (EC) and better description was found when the removal experimental data were matched with a model including liquid axial dispersion in contrast to an ideal plug flow model.