Effect of nitrogen limitation on performance of toluene degrading biofilters

The literature reports conflicting observations regarding the need for nutr ient addition to biofilters treating contaminated gases. Such conflicts are often based on quasi-steady-state performance data collected on biofilters operated under continuous loading conditions. In the studies described her ein, the impact of nitrogen limitations on two toluene-fed biofilters was a ssessed over a 97-day period. The biofilters were packed with polyurethane foam medium and contained different initial levels of nitrate-nitrogen. Tol uene and CO2 concentration profiles were monitored during both normal stead y loading conditions and short-term, unsteady-slate transient loading condi tions (e.g., shock loads). Packing medium samples were periodically removed and analyzed to quantify changes in nitrate-nitrogen content over time. Da ta are presented which show that over long-time periods (several months), n utrient-induced kinetic limitations diminished biofilter performance during transient, unsteady-state conditions even when performance during normal s teady loading was not adversely affected. Elemental analysis of biomass rem oved from the biofilters support nitrate-nitrogen and CO2 concentration pro file data and clearly illustrate how kinetically limited biofilters fail du ring shock loads even when there is an overall stoichiometric excess of nut rients. (C) 2001 Elsevier Science Ltd. All rights reserved.