Sequencing batch biofilter operation for treatment of methyl ethyl ketone (MEK) contaminated air

Biofiltration is increasingly used as a method for decontaminating gas streams containing low concentrations of biodegradable volatile organic compounds. In typical biofilter installations, control is quite passive and is often restricted to adjustment of the medium's moisture content or nutrient supply. Although inexpensive, such operation limits implementation of engineering decisions that could improve performance during normal operation or allow effective handling of the short-term variations in the waste stream typical of industrial operations. This paper describes how sequencing batch operation can be applied to biofilters designed and operated as controlled, unsteady-state, periodic processes for the destruction of gas-phase contaminants. In the studies described herein, the impact of sequencing batch operation was assessed in a methyl ethyl ketone degrading biofilter over a 130-day period. The biofilter was packed with a polyurethane foam medium that contained activated carbon. Methyl ethyl ketone and carbon dioxide concentrations were monitored during both normal steady loading conditions and short-term, unsteady-state transient loading conditions (i.e., shock loading). A gas stream containing 106 ppm(v) methyl ethyl ketone was used for normal loading studies, and several model shock loads consisting of 530 ppm(v) methyl ethyl ketone for a duration of one hour were used to assess system response to transient loads. Data are presented which clearly demonstrate that sequencing batch operation can be successfully applied to biofilters treating methyl ethyl ketone contaminated air streams. Such operation can increase an operator's ability to minimize contaminant emission during transient periods of elevated contaminant loading.